CN111040742B - Shale inhibitor and preparation method thereof, drilling fluid and application thereof - Google Patents

Abstract

The invention relates to the field of oilfield chemistry, and discloses a shale inhibitor, a preparation method thereof, a drilling fluid and application thereof. The shale inhibitor is composed of a structural unit represented by formula (1) and a structural unit represented by formula (2). , wherein the molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) is 0.1-7:1; and the weight-average molecular weight of the shale inhibitor is 2000-15000 g/mol . The preparation method of the shale inhibitor comprises: in the presence of a basic compound, carrying out an amidation reaction of glycine and arginine; the molar ratio of the amount of glycine and arginine is 0.1-6:1; the amidation reaction The conditions are such that the weight-average molecular weight of the obtained polymer is 2000-15000 g/mol. The shale inhibitor provided by the invention can effectively inhibit the hydration expansion and dispersion of shale, and has good temperature resistance.

Description

Shale inhibitor and preparation method thereof, drilling fluid and application thereof

technical field

The invention relates to the field of oilfield chemistry, in particular to a shale inhibitor, a preparation method thereof, a drilling fluid and application thereof.

Background technique

With the exploration and development of domestic oil and gas resources, the potential of conventional oil and gas resources is decreasing day by day. The exploration and development of unconventional oil and gas reservoirs has become the focus in China, and the development of shale formation oil and gas reservoirs is one of the research priorities. Shale formations account for about 75% of drilled reservoirs, and more than 90% of wellbore stability problems occur in shale formations. When water-based drilling fluids are used in the drilling process of shale formations, shale hydration and expansion will inevitably occur, resulting in borehole shrinkage, sticking, instability of the borehole wall, and prone to accidents such as well collapse, increasing the number of drilling operations. Time and construction costs, so oil-based drilling fluids are often used in shale formations. However, the cost and environmental problems of oil-based drilling fluids are prominent. Once a lost circulation occurs, the cost will be greatly increased. With the increasing emphasis on environmental protection at home and abroad, the importance of environmentally friendly drilling fluid systems has been continuously increased. Therefore, high-performance water-based drilling fluids Drilling fluids have been paid more and more attention and many studies have been carried out.

Shale inhibitors are essential as the core treatment agent of high-performance water-based drilling fluids. Over the past few decades, industry workers have developed various inhibitors, which can be simply divided into the following categories according to their mode of action:

(1) Reduced water activity type

Due to the great chemical potential difference between the formation near the wellbore and the drilling fluid, water molecules will flow from the drilling fluid with high activity to the nearby wellbore with low activity, which will cause the mud shale near the wellbore to swell with water. , causing the shaft wall to become unstable. Reducing the water activity of the drilling fluid through inhibitors can effectively prevent or delay the migration of water molecules from the drilling fluid to the formation, thereby reducing the hydration of shale. Such inhibitors are mainly inorganic salts.

Sodium chloride saturated solution has high viscosity and low activity, which can effectively reduce the immersion of drilling fluid filtrate into the formation, and when used in combination with other treatment agents, it can also lead to shale dehydration. Divalent inorganic salt solutions such as calcium chloride have low activity, which can reduce the invasion of drilling fluid filtrate into the formation to a certain extent. Stable, so it needs to be considered comprehensively. The saturated solution activity of formate and organic salts is low, which can generate a large osmotic pressure difference, prevent the migration of water to the formation, and improve the stability of the wellbore. At the same time, potassium ion itself also has a strong inhibitory effect.

(2) Improve the quality of filter cake

The filtrate loss of drilling fluid is closely related to the viscosity of the drilling fluid and the quality of the mud cake (mud cake permeability). .

Humic acid and its derivatives, starch and its derivatives, cellulose, etc. themselves contain colloidal components, which can protect the clay particles, significantly improve the quality of the mud cake, reduce the permeability of the mud cake, and thus exert its inhibit performance.

(3) Increased liquid viscosity type

From a broad point of view, any treatment agent that can increase the viscosity of the filtrate and reduce the filtration loss is this type of inhibitor. Sugars and their derivatives and other viscosifiers can increase the viscosity of the filtrate, reduce the water activity, and prevent the migration of water molecules to the formation near the borehole wall. Such as methyl glucoside, it is mainly added to the drilling fluid to exert inhibition through viscosification.

(4) Sealing fissure type

Asphalt inhibitors are mainly divided into oxidized asphalt and sulfonated asphalt. Oxidized bitumen has a softening point and can be deformed under specific temperature and pressure conditions to block formation cracks. In addition, it can form a protective film on the wellbore to prevent water from migrating from drilling fluid to the formation. The oil-soluble part of the sulfonated asphalt can enter the formation for plugging under a certain pressure difference, and the water-soluble sulfonic acid groups can be adsorbed on the clay crystal layer to inhibit the hydration and dispersion of the clay. Polymeric alcohol inhibitors have cloud point effect. After entering the formation, when the temperature is higher than the cloud point, microemulsion will be formed, and under the action of pressure difference, it will enter the wellbore fractures for plugging, and at the same time, a hydrophobic film can be formed on the wellbore to stabilize the well. wall.

(5) Change the wettability type

The clay surface is hydrophilic, which is the essential reason for its hydration expansion. Therefore, changing the wettability of the clay surface can effectively inhibit the hydration expansion of clay and improve the stability of shale. Since the clay surface is negatively charged, cationic surfactants have the strongest ability to change the wettability of the clay surface. For example, dodecyl trimethyl chloride and dodecyl pyridine chloride can be adsorbed on the clay surface through the cationic or polar end part, and the non-polar end can cover the surface of the clay particles, reducing the hydrophilicity of the clay. , and even become oleophilic, preventing water from entering the formation. Organosilicon can undergo polycondensation with the clay surface to generate Si-O-Si bonds, invert the wettability of the clay surface to hydrophobicity, and reduce the adsorption of water molecules on the clay surface.

(6) Reduce hydration energy type

Clay will cause surface hydration due to its own exchangeable cations with strong hydration energy, so replacing exchangeable cations with cations with lower hydration energy can effectively inhibit surface hydration. Potassium ions are easily embedded in the six-membered ring of oxygen atoms between adjacent layers and are not easily replaced. The hydration energy is low and the hydration radius is small, making it a widely used inhibitor. The greater impact is gradually replaced. In addition to potassium ions, ammonium ions, low molecular organic cations such as glycidyl trimethyl ammonium chloride can also play a similar role.

(7) Bridge coated type

Bridge-coated inhibitors are mainly high molecular polymers. It mainly plays the role of stabilizing shale through adsorption, bridging and coating. On the one hand, polymers can block micro-cracks and prevent shale hydration through multi-point adsorption; on the other hand, polymers can form a protective film on the well wall to prevent water molecules from entering the formation. The inhibitory effect is related to the polymer adsorption group, hydration group, molecular weight and other factors.

(8) chemical cementation

Since the solubility of aluminum-based compounds and silicates is related to the pH value of the environment, after entering the formation, the solubility decreases under specific pH conditions, resulting in colloidal precipitation, which blocks the formation pores.

At present, there are many kinds of inhibitors used in oil fields, and there are differences and deficiencies in the performance of each kind. Potassium ions can effectively inhibit shale expansion, but their use concentration is high, which has a greater impact on the environment; amines are greatly affected by pH; high molecular weight diamines have poor solubility in water, while high molecular weight monoamines inhibit Low molecular weight diamine has toxicity and odor; polyethoxydiamine has the characteristics of low toxicity and low ammonia odor, but its shale inhibition ability is worse than that of general inhibitors. The polyalcohol-based shale inhibitor needs to match the formation temperature, and its inhibitory performance is not strong. Although environmental-friendly inhibitors are being vigorously developed at home and abroad, the current environmental-friendly inhibitors cannot completely replace polyamine inhibitors. Therefore, it is urgent to introduce new materials and develop new water-based drilling fluid shale inhibitors to meet the needs of exploration and development. At present, many scholars at home and abroad have carried out a lot of exploration: An et al. introduced chitosan quaternary ammonium salt into water-based drilling fluid, and systematically evaluated the inhibitory effect of chitosan quaternary ammonium salt through linear expansion, rolling recovery, and inhibition of pulping experiments. , the results show that chitosan quaternary ammonium salt can be used as an environmentally friendly inhibitor against high temperature. Gou et al. synthesized a series of ionic liquid/polyethylene glycol inhibitors with good anti-swelling rate and environmental performance. Glebe et al. independently synthesized the hyperbranched polyglycerol inhibitor and compounded it with KCl. The indoor evaluation showed that the inhibitory ability of the system could be improved. Aghil et al. evaluated the ability of triterpenoid saponins to inhibit clay swelling, and laboratory tests showed that the natural surfactant has the ability to inhibit clay hydration swelling.

In conclusion, the development of efficient and environmentally friendly water-based drilling fluid inhibitors is not only an essential material for constructing high-performance water-based drilling fluids, but also conducive to promoting the efficient and clean development of drilling fluids.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects that the shale inhibitor performance of the existing drilling fluid is not ideal and the shale inhibitor contained in the shale inhibitor is environmentally harmful, and to provide a shale inhibitor with high shale inhibitor performance and environmental protection and preparation method thereof, as well as drilling fluid containing the shale inhibitor and application thereof. The shale inhibitor provided by the invention can effectively inhibit the hydration expansion and dispersion of shale, and has good temperature resistance.

In order to achieve the above object, a first aspect of the present invention provides a shale inhibitor, the shale inhibitor is composed of a structural unit represented by formula (1) and a structural unit represented by formula (2),

The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) is 0.1-7:1; and the weight average molecular weight of the shale inhibitor is 2000-15000 g/mol.

A second aspect of the present invention provides a method for preparing a shale inhibitor, the method comprising: carrying out an amidation reaction between glycine and arginine in the presence of a basic compound; the molar ratio of the glycine and arginine is: 0.1-6:1; the amidation reaction conditions are such that the weight-average molecular weight of the obtained polymer is 2000-15000 g/mol.

A third aspect of the present invention provides a shale inhibitor prepared by the above preparation method.

A fourth aspect of the present invention provides a drilling fluid, wherein the drilling fluid contains the above-mentioned shale inhibitor or the shale inhibitor prepared by the above-mentioned preparation method.

The fifth aspect of the present invention provides the application of the above drilling fluid in the stabilization of shale wellbore.

The present invention uses a polyamino acid composed of structural units of glycine and arginine in a specific molar ratio, and selects the polyamino acid within a specific weight-average molecular weight range as the shale inhibitor of the present invention, thereby making the shale inhibitor It can effectively inhibit the hydration expansion and dispersion of clay, and has good high temperature resistance; and the shale inhibitor of the present invention is easy to enter the nano-scale pores of mud shale and adsorb on the surface of clay minerals, so as to better compress clay Surface electric double layer, reducing clay swelling pressure and preventing wellbore instability caused by clay swelling. In addition, the shale inhibitor provided by the present invention can perform biodegradation well after effectively inhibiting the instability of shale, and has good environmental protection performance.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise ranges or values, which are to be understood to encompass values proximate to those ranges or values. For ranges of values, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values can be combined with each other to yield one or more new ranges of values that Ranges should be considered as specifically disclosed herein.

A first aspect of the present invention provides a shale inhibitor, the shale inhibitor is composed of a structural unit represented by formula (1) and a structural unit represented by formula (2),

The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) is 0.1-7:1; and the weight average molecular weight of the shale inhibitor is 2000-15000 g/mol.

In the present invention, the weight average molecular weight of the shale inhibitor is 2000-15000 g/mol, preferably 4000-8000 g/mol. By making the weight average molecular weight of the shale inhibitor of the present invention within the above range, on the one hand, the shale inhibitor can have a higher adsorption capacity and adsorption strength on the shale surface, and effectively wrap the shale; On the other hand, it can enter between the shale crystal layers, reduce the crystal layer spacing, and reduce water intrusion. The measurement of the weight-average molecular weight in the present invention is carried out according to the method described in the examples described later.

所示的结构单元具有甘氨酸的主体化学结构，式(2)

所示的结构单元具有精氨酸的主体化学结构，因此，实际上本发明的页岩抑制剂是一种二元聚氨基酸(即甘氨酸和精氨酸的缩合肽)。本发明选用式(1)所示的结构单元和式(2)所示的结构单元来构成本发明的页岩抑制剂，是因为一方面，式(1)所示的结构单元和式(2)所示的结构单元为氨基酸的结构，能够易于被微生物所降解，因此可以定义为一种可降解页岩抑制剂；另一方面，式(1)所示的结构单元相对的更易熔融聚合，有助于提高聚合物分子量，式(2)所示的结构单元为含碱性胍基的氨基酸，即使在碱性很强的介质中，也含有带正电的亲水氨基，可使聚合物在碱性条件下仍具有较强的抑制效果；将式(1)所示的结构单元和式(2)所示的结构单元的组合能够形成具有一定分子量的阳离子型聚合物，在保持可降解性的同时，具有优异的抑制效果。In the present invention, formula (1)

The structural unit shown has the host chemical structure of glycine, formula (2)

The structural unit shown has the main chemical structure of arginine, therefore, the shale inhibitor of the present invention is actually a dimeric polyamino acid (ie, a condensed peptide of glycine and arginine). The present invention selects the structural unit represented by the formula (1) and the structural unit represented by the formula (2) to constitute the shale inhibitor of the present invention, because on the one hand, the structural unit represented by the formula (1) and the formula (2) ) is an amino acid structure, which can be easily degraded by microorganisms, so it can be defined as a degradable shale inhibitor; on the other hand, the structural unit shown in formula (1) is relatively easier to melt and polymerize, It is helpful to increase the molecular weight of the polymer. The structural unit represented by the formula (2) is an amino acid containing a basic guanidine group. Even in a strong alkaline medium, it also contains a positively charged hydrophilic amino group, which can make the polymer It still has a strong inhibitory effect under alkaline conditions; the combination of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) can form a cationic polymer with a certain molecular weight, which can be degraded while maintaining At the same time, it has excellent inhibitory effect.

In the present invention, the terminal of the polymer composed of the structural unit represented by the above formula (1) and the structural unit represented by the formula (2) is not particularly limited, and can be a conventional group, such as H, a hydroxyl group, or a formed salt, etc. .

The present invention does not specifically limit the structure of the dibasic polyamino acid, and it can be a regular block copolymer, a partially regular block copolymer and a random copolymer. In order to avoid the cumbersome production process, the The rock inhibitor is preferably a random copolymer.

According to a preferred embodiment of the present invention, the molar ratio of the structural unit represented by formula (1) and the structural unit represented by formula (2) is 0.1-3:1, more preferably 0.1-2:1, and further Preferably it is 0.5-1.5:1.

According to a preferred embodiment of the present invention, the molecular weight distribution index Mw/Mn of the shale inhibitor is 1.5-11.6, preferably 2-10, more preferably 4-6. The measurement of the molecular weight distribution index of the shale inhibitor was carried out according to the method described in the following Examples.

A second aspect of the present invention provides a method for preparing a shale inhibitor, the method comprising: carrying out an amidation reaction between glycine and arginine in the presence of a basic compound; the molar ratio of the glycine and arginine is: 0.1-6:1; the amidation reaction conditions are such that the weight-average molecular weight of the obtained polymer is 2000-15000 g/mol.

According to the preparation method provided by the present invention, the raw materials of the glycine and arginine are widely selected, and the above glycine can be provided by glycine hydrochloride; the above arginine can be L-type, D-type or a mixture of the two , the above arginine can be provided by arginine hydrochloride.

According to the present invention, the amount of glycine and arginine can be selected in a wide range, as long as the weight-average molecular weight of the amidation reaction product can be 2000-15000 g/mol, for example, the glycine and arginine The molar ratio of the amount of acid used is 0.1-6:1, preferably 0.1-3:1, more preferably 0.1-2:1, still more preferably 0.5-1.5:1.

According to the present invention, the amidation reaction is carried out in the presence of a basic compound, and the present invention has a wide range of types of the basic compound, subject to the basic environment that can provide the reaction, such as sodium methoxide, methanol One or more of potassium, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, sodium hydroxide, potassium hydroxide and lithium hydroxide, etc., preferably the one in sodium hydroxide, potassium hydroxide and lithium hydroxide or more, particularly preferably sodium hydroxide. The preparation method of the shale inhibitor provided by the present invention is carried out in the presence of an alkaline compound, rather than in an acidic condition. Since the pH value of drilling fluid is generally maintained in the alkaline range of 8-11, the product is acidic when using inorganic acid, which is not suitable for drilling fluid; if the reaction is carried out in the presence of inorganic acid, the pH value is adjusted to When alkaline, the inhibitor effect will be reduced.

According to the present invention, the basic compound may be in the form of a solution of the basic compound, preferably, the concentration of the solution of the basic compound is 1-10 mol/L. The solvent in the solution of the basic compound may be water.

According to a preferred embodiment of the present invention, the molar ratio of the basic compound to the total amount of glycine and arginine is 0.1-0.3:1, preferably 0.15-0.25:1.

According to a particularly preferred embodiment of the present invention, in the presence of a basic compound, glycine and arginine are subjected to an amidation reaction; the molar ratio of the amount of glycine and arginine is 0.5-1.5:1; the basic The compound is sodium hydroxide, and the molar ratio of the sodium hydroxide to the total amount of glycine and arginine is 0.15-0.25:1. By adopting this preferred embodiment, a shale inhibitor with better performance can be obtained.

According to the present invention, the conditions for the amidation reaction are not particularly limited, as long as the weight-average molecular weight of the obtained polymer is 2000-15000 g/mol (preferably 4000-8000 g/mol), it can be used in the field of The amidation reaction is carried out under conventional conditions for the synthesis of amino acid polymers. Preferably, the amidation reaction conditions include: a temperature of 180-230° C. and a time of 1-8 h. More preferably, the conditions of the amidation reaction include: a temperature of 190-230° C. and a time of 2-4 h. Further preferably, the temperature is 200-230°C.

According to a specific embodiment of the present invention, the amidation reaction can be carried out in a muffle furnace.

According to the present invention, in order to meet application requirements, the method may further comprise pulverizing (eg, grinding) the product obtained by the amidation reaction.

A third aspect of the present invention provides the shale inhibitor prepared by the above preparation method.

According to the present invention, the shale inhibitor prepared by the above preparation method is a mixture of a copolymer of glycine and arginine, except that the weight average molecular weight of the copolymer of glycine and arginine is 2000-15000 g/mol. within the range. Other parameters of the shale inhibitor are as described above, and will not be repeated here.

A fourth aspect of the present invention provides a drilling fluid containing the above shale inhibitor or the shale inhibitor prepared by the above method for preparing the shale inhibitor.

According to the present invention, the shale inhibitor can greatly improve the stability of the wellbore when the drilling fluid is used for drilling. Preferably, in the drilling fluid, the content of the shale inhibitor is 0.5-2 wt %, more preferably 1-2 wt %.

The present invention has no particular limitation on the drilling fluid system containing the shale inhibitor, and can be various conventional drilling fluid systems in the art, as long as the shale inhibitor of the present invention is added to these conventional drilling fluid systems. As such a conventional drilling fluid system, for example, it can be one or more of potassium chloride-polyacrylamide drilling fluid, polyalcohol drilling fluid and organic silicon drilling fluid. The potassium chloride-polyacrylamide drilling fluid can be various potassium chloride-polyacrylamide drilling fluids known to those skilled in the art, such as potassium chloride-hydrolyzed polyacrylamide drilling fluid, potassium chloride- One or more of cationic polyacrylamide drilling fluid, potassium chloride-amphoteric polyacrylamide drilling fluid and potassium chloride-polyacrylic acid drilling fluid; A kind of polymer alcohol drilling fluid, for example, can be one or more of polyethylene glycol drilling fluid, polypropylene glycol drilling fluid, ethylene glycol/propylene glycol copolymer drilling fluid, polyglycerol drilling fluid and polyethylene glycol drilling fluid The organosilicon drilling fluid can be various organosilicon drilling fluids well known to those skilled in the art, and the organosilicon in the organosilicon drilling fluid can be selected from sodium methylsiliconate, potassium methylsiliconate and One or more of the silicone potassium humate.

According to the present invention, the drilling fluid is preferably a water-based drilling fluid, that is, a multiphase dispersion system composed of water as the main matrix and adding various additives. Further, the present invention is preferably a polymer drilling fluid, and only the shale inhibitor of the present invention provides cations (instead of the usual 2,3-epoxypropyltrimethylammonium chloride, 3-chloro -2-hydroxypropyltrimethylammonium chloride or cationic polyacrylamide, etc. to provide cations).

The above-mentioned polymer drilling fluid using the shale inhibitor of the present invention as a cation may contain other additives as the polymer drilling fluid. Preferably, the drilling fluid of the present invention contains bentonite, tackifier, anti-slump agent, filter reducing agent One or more of loss agent, plugging agent, potassium chloride, calcium carbonate, barium sulfate and alkali metal hydroxide.

Wherein, the bentonite refers to the clay with montmorillonite as the main mineral component, which has the function of imparting viscosity and shear force to the drilling fluid and fluid loss and wall-building properties, such as sodium-based bentonite and/or calcium-based bentonite, preferably Sodium Bentonite. More preferably, the content of the bentonite is 2-4 wt %, more preferably 3-4 wt %.

Wherein, the tackifier can improve the viscosity and shear force of drilling fluid, such as potassium polyacrylamide (KPAM), polyanionic cellulose (such as PAC141) and copolymer of acrylamide and sodium acrylate (such as 80A51) One or more of them, preferably polyacrylamide potassium salt. More preferably, the content of the tackifier is 0.2-0.5% by weight, more preferably 0.3-0.5% by weight.

Wherein, the anti-slump agent can assist the shale inhibitor to prevent the collapse of the wellbore and improve the stability of the wellbore, such as potassium humate (KHM), organosilicon (for example, GF-1) and sulfonated asphalt (For example, one or more of the brand name is FT-1A), preferably potassium humate. More preferably, the content of the anti-slump agent is 2-4% by weight.

Wherein, the filtrate reducer can improve the filtration loss and wall-building properties of drilling fluid, for example, it can be sulfomethyl phenolic resin (for example, the brand is SMP-I, SMP-II), sulfomethyl lignite resin (for example, the brand is SPNH) One or more of , modified starch and zwitterionic polymer JT-888, preferably modified starch. More preferably, the content of the fluid loss control agent is 1-8 wt %, more preferably 3-5 wt %.

Among them, the plugging agent can improve the wall-building performance and leakage performance of drilling fluid filtration, and prevent the wellbore instability and lost circulation. For example, it can be ultrafine calcium carbonate, white asphalt, nano-silica and walnut. One or more of the shells, preferably ultrafine calcium carbonate and white pitch. More preferably, the content of the plugging agent is 3-9% by weight.

Various substances of the above-mentioned additives can be commercially available products, and can also be prepared according to conventional methods in the art, which will not be repeated here.

In the drilling fluid of the present invention, preferably, the content of potassium chloride is 3-5% by weight. Preferably, the content of calcium carbonate is 3-5% by weight. Preferably, the content of barite is 10-20% by weight (for example, it can be barite with a barium sulfate content of more than 90% by weight). Preferably, the content of alkali metal hydroxide is 0.1-0.4% by weight, more preferably 0.1-0.2% by weight (as a component of drilling fluid, the alkali metal hydroxide here has the effect of improving the pulping performance of bentonite, and can is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide, preferably sodium hydroxide).

In a preferred embodiment of the present invention, a drilling fluid is provided, the drilling fluid contains 1-2 wt % of the shale inhibitor, 3-4 wt % of bentonite, 0.3-0.5 wt % % polyacrylamide potassium salt, 2-4 wt % potassium humate, 3-5 wt % modified starch, 3-5 wt % white asphalt, 3-4 wt % ultrafine calcium carbonate, 3 -5wt% potassium chloride, 10-20wt% barite, 0.1-0.2wt% sodium hydroxide, balance water.

The fifth aspect of the present invention also provides the application of the above drilling fluid in the stabilization of shale wellbore.

When the above drilling fluid is used in the stabilization of shale wellbore, it can effectively maintain the stability of the wellbore by inhibiting the hydration expansion of the clay in the shale and reducing the electric double layer repulsion of the adjacent clay in the pores of the shale. .

The present invention will be described in detail below by means of examples.

In the following examples and comparative examples, the weight-average molecular weight is measured by GPC gel chromatography (the experimental instrument is a gel chromatograph from American waters company, the model is E2695); the molecular weight distribution index is the weight obtained by using GPC gel chromatography. The ratio of average molecular weight to number average molecular weight.

Example 1

This example is used to illustrate the shale inhibitor of the present invention and its preparation method.

Weigh 2.5g (0.022mol) glycine hydrochloride (Gly) and 7.5g (0.036mol) arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; then add 1g mass fraction to the watch glass 50% aqueous NaOH solution, and mix with stirring. Subsequently, the mixture was moved into a muffle furnace and reacted at 200° C. for 3 h to obtain a dark brown solid product, which was cooled and ground to obtain an inhibitor (PGA-1). The weight-average molecular weight _Mw measured by gel permeation chromatography was 7500 g/mol, and the molecular weight distribution index was 5.5. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 0.69:1 according to the analysis of the hydrogen NMR spectrum and the carbon spectrum.

Example 2

This example is used to illustrate the shale inhibitor of the present invention and its preparation method.

Weigh 0.8g (7.2×10 ^-3 mol) glycine hydrochloride (Gly) and 7.5g (0.036mol) arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; Add 1 g of a 50% NaOH aqueous solution, and mix and stir. Subsequently, the mixture was moved into a muffle furnace, and after reacting at 215° C. for 2 h, a dark brown solid product was obtained, and then the obtained product was cooled and ground to obtain an inhibitor (PGA-2). The weight-average molecular weight _Mw measured by gel permeation chromatography was 2200 g/mol, and the molecular weight distribution index was 10.5. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 0.22:1 from the analysis of the hydrogen NMR spectrum and the carbon spectrum.

Example 3

This example is used to illustrate the shale inhibitor of the present invention and its preparation method.

Weigh 1.6g (0.0144mol) of glycine hydrochloride (Gly) and 7.5g (0.036mol) of arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; then add 1g mass fraction to the watch glass 50% aqueous NaOH solution, and mix with stirring. Subsequently, the mixture was moved into a muffle furnace and reacted at 200° C. for 4 h to obtain a dark brown solid product, which was then cooled and ground to obtain an inhibitor (PGA-3). The weight-average molecular weight _Mw measured by gel permeation chromatography was 3500 g/mol, and the molecular weight distribution index was 6.8. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 0.45:1 from the analysis of the hydrogen NMR spectrum and the carbon spectrum.

Example 4

Weigh 7.5g (0.067mol) of glycine hydrochloride (Gly) and 2.5g (0.012mol) of arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; then add 1g mass fraction to the watch glass 50% aqueous NaOH solution, and mix with stirring. Subsequently, the mixture was moved into a muffle furnace, and after reacting at 190° C. for 3 h, a dark brown solid product was obtained, and then the obtained product was cooled and ground to obtain an inhibitor (PGA-4). The weight-average molecular weight _Mw measured by gel permeation chromatography was 8500 g/mol, and the molecular weight distribution index was 4.2. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 6.7:1 according to the analysis of the hydrogen nuclear magnetic resonance spectrum and the carbon spectrum.

Example 5

This example is used to illustrate the shale inhibitor of the present invention and its preparation method.

Weigh 2.5g (0.022mol) glycine hydrochloride (Gly) and 7.5g (0.036mol) arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; then add 1g mass fraction to the watch glass 50% aqueous NaOH solution, and mix with stirring. Subsequently, the mixture was moved into a muffle furnace, and after reacting at 190° C. for 3 h, a dark brown solid product was obtained, and then the obtained product was cooled and ground to obtain an inhibitor (PGA-5). The weight-average molecular weight _Mw measured by gel permeation chromatography was 4300 g/mol, and the molecular weight distribution index was 7.4. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 0.72:1 according to the analysis of the hydrogen nuclear magnetic resonance spectrum and the carbon spectrum.

Example 6

Weigh 7.5g (0.067mol) of glycine hydrochloride (Gly) and 2.5g (0.012mol) of arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; then add 1g mass fraction to the watch glass 50% aqueous NaOH solution, and mix with stirring. Subsequently, the mixture was moved into a muffle furnace, and after reacting at 220° C. for 3 h, a dark brown solid product was obtained, and the obtained product was cooled and ground to obtain an inhibitor (PGA-6). The weight-average molecular weight _Mw measured by gel permeation chromatography was 12000 g/mol, and the molecular weight distribution index was 4.1. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 5.9:1 from the analysis of the hydrogen NMR spectrum and the carbon spectrum.

Example 7

According to the method of Example 1, the difference is that the dosage of glycine hydrochloride (Gly) is 0.022 mol, and the dosage of arginine hydrochloride (Arg) is 0.015 mol to obtain inhibitor (PGA-7). The weight-average molecular weight _Mw measured by gel permeation chromatography was 6100 g/mol, and the molecular weight distribution index was 4.9. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 1.5:1 according to the analysis of the hydrogen nuclear magnetic resonance spectrum and the carbon spectrum.

Comparative Example 1

Weigh 2.5g (0.022mol) of glycine hydrochloride (Gly) and 7.5g (0.036mol) of arginine hydrochloride (Arg), add them to the watch glass in turn, mix and stir; then add 0.25g mass to the watch glass Fraction is 50% NaOH aqueous solution, and mix and stir. Subsequently, the mixture was moved into a muffle furnace and reacted at 180° C. for 2 h to obtain a dark brown solid product, which was cooled and ground to obtain the inhibitor (D-1). The weight-average molecular weight _Mw measured by gel permeation chromatography was 950 g/mol, and the molecular weight distribution index was 2.7. The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the obtained polymer was found to be 0.83:1 according to the analysis of the hydrogen nuclear magnetic resonance spectrum and the carbon spectrum.

Comparative Example 2

The method of Example 1 was followed, except that glycine hydrochloride was replaced with an equimolar amount of lysine. The inhibitor (D-2) was obtained. The weight-average molecular weight _Mw measured by gel permeation chromatography was 1450 g/mol, and the molecular weight distribution index was 4.9.

Test Example 1

A linear expansion experiment was performed on the inhibitors obtained in the above examples and comparative examples, including: evaluating the expansion amount of bentonite by means of a shale dual-channel linear dilatometer. Put 5g of bentonite into the sleeve of the instrument and press at 10MPa for 5min; then put a layer of filter paper on the pressed bentonite block to ensure the uniform expansion of the clay; insert the sleeve into the dilatometer, and add 20ml of water or water to the inner groove of the sleeve. Inhibitor solution, record the swelling amount of the bentonite block with time, the experimental results of the swelling amount after 24h are listed in Table 1.

The inhibition effect of different inhibitors was compared through the linear expansion experiment. The lower the clay swelling amount, the better the inhibition effect. It can be seen from Table 1 below that bentonite can undergo severe hydration expansion in water, and the expansion amount reaches 6.49mm after 24h. After adding PGA series inhibitors, the swelling amount decreased to varying degrees.

It can be seen from the results in Table 1 that PGA-1 exhibited the lowest linear expansion height and the best inhibition effect.

Table 1 Linear expansion height of different inhibitors

Test Example 2

Rolling recovery experiments were carried out on the inhibitors obtained in the above examples and comparative examples, including:

Weigh 20g of 6-10 mesh shale cuttings, prepare 350ml of inhibitor solution with a certain concentration at the same time, pour the inhibitor solution and cuttings into the aging kettle; then seal the aging kettle and put it into the high temperature roller furnace Inside, heat rolling at 150 °C for 16 hours; after aging, take out the aging kettle and cool it to room temperature, filter the cuttings in the dispersion with a 40-mesh screen and wash repeatedly, and dry and weigh the remaining cuttings. The shale recovery rate was calculated by the mass ratio of drill cuttings before and after aging, and the results are listed in Table 2. The calculation formula of shale recovery rate is as follows:

Among them, m ₁ is the mass of cuttings before aging, g; m ₂ is the mass of remaining cuttings after aging, g.

Table 2 Rolling recoveries of different inhibitors

The ability of the inhibitor to inhibit the hydration and dispersion of cuttings was evaluated by the rolling recovery experiment. The higher the rolling recovery rate, the better the inhibition effect. It can be seen from Table 2 that the results of the rolling recovery test are consistent with the results of the linear expansion test. In clean water, the recovery rate of cuttings was only 20.25%, and the hydration and dispersion were serious; after adding the inhibitor, the recovery rate of cuttings was improved to varying degrees. The recovery rate was the highest after adding PGA-1, showing the best inhibitory effect. At the same time, the recovery rate of PGA-1 after hot rolling at 150 °C can still reach more than 80%, showing good temperature resistance.

Test Example 3

The particle size analysis of the bentonite particle size after the action of different inhibitors is carried out by a laser particle size analyzer, including:

Disperse 4g of bentonite into 100ml of deionized water, stir indoors for 24h and then stand for 24h to prepare a bentonite base slurry. Take 20ml of bentonite base slurry, add a certain quality of inhibitor and stir for 12h to make it fully mixed; take the bentonite dispersion after adding the inhibitor, and measure its particle size distribution by a laser particle size analyzer wet method, the results are listed in Table 3 . It can be seen from the table below that in clean water, the clay particles hydrate and swell and disperse into smaller particles; after adding the inhibitor, the coalescence of the clay particles increases. The PGA inhibitor provided by the present invention contains functional groups such as amino group and guanidine group. These functional groups are alkaline after being dissolved in water, and some amino groups are positively charged due to protonation reaction. PGA molecules can be adsorbed on hydrogen bonds and electrostatic neutralization. The surface of the negatively charged clay particles forms multi-point adsorption, bridges and wraps the clay particles, and makes the clay particles agglomerate and become larger.

Table 3 Particle size of bentonite under the action of different inhibitors

sample Bentonite volume average particle size/μm under 2 wt% inhibitor addition Shimizu 7.523 PGA-1 65.737 PGA-2 33.952 PGA-3 42.873 PGA-4 35.145 PGA-5 53.351 PGA-6 39.354 PGA-7 60.728 D-1 15.233 D-2 30.519

Test Example 4

The interlayer spacing of bentonite under the action of different inhibitors was analyzed, including:

加入抑制剂后，黏土晶层间距不同程度地下降，其中PGA-1的晶层间距最低。实验结果表明，PGA抑制剂分子可以进入黏土晶层，降低黏土晶层间距，排除水分子，抑制黏土水化膨胀。Disperse 4g of bentonite into 100ml of deionized water, stir indoors for 24h and then stand for 24h to prepare a bentonite base slurry. Take 20ml of bentonite base slurry, add a certain quality of inhibitor and stir for 12h to make it fully mixed; take the bentonite dispersion after adding the inhibitor, centrifuge at 8000r/min for 15min, pour off the supernatant, and remove the lower bentonite precipitate , the X-ray diffraction pattern was measured by an X-ray diffractometer and the interlayer spacing was calculated. The results are listed in Table 4. It can be seen from the table below that after the clay is hydrated and expanded, water molecules enter the interlayers of the clay crystals, which increases the interlayer spacing. The change in the interlayer spacing of the clay crystals can be measured by X-ray diffraction experiments to evaluate the effect of the inhibitor. It can be seen from the table below that the interlayer spacing of clay in water measured in this experiment is

After adding the inhibitor, the interlayer spacing of clay decreased to varying degrees, and the interlayer spacing of PGA-1 was the lowest. The experimental results show that the PGA inhibitor molecules can enter the clay crystal layer, reduce the spacing between the clay crystal layers, exclude water molecules, and inhibit the hydration and swelling of the clay.

Table 4 Interlayer spacing of bentonite after different inhibitors

Application Examples 1-7

The water-based drilling fluid is prepared according to the following formula: 3 wt % sodium bentonite (purchased from Shandong Weifang Huawei Bentonite Company), 0.2 wt % NaOH, 0.5 wt % KPAM (purchased from Wulian Chemical Factory, Pingxiang City, Jiangxi Province, trade name Helian/K-PAM, the same below), 4% by weight KHM (purchased from Jiangxi Pingxiang City Boxin Industrial Co., Ltd., the same below), 4% by weight of modified starch (purchased from Beijing Shida Bocheng Technology Co., Ltd., below same), 4% by weight of white asphalt (purchased from Beijing Shida Bocheng Technology Co., Ltd., the same below), 3% by weight of potassium chloride, 3% by weight of calcium carbonate, 10% by weight of barite (the barite The barium sulfate content is 93% by weight, purchased from Shandong Lingshou County Xingwang Mineral Products Processing Plant, the same below), and respectively adding 1% by weight of the shale inhibitors of Examples 1-7, and the balance is water, thereby obtaining Drilling fluids A1-A7.

Application Comparative Example 1-2

According to the formula described in Application Example 1, the difference is that 1% by weight of the shale inhibitor prepared in Comparative Examples 1-2 was added to replace the shale inhibitor in Example 1, thereby preparing drilling fluids DA1-DA2 .

Test Example 1

The plastic viscosity, dynamic shear force, API fluid loss, HTHP fluid loss, and hot rolling recovery of drilling fluids A1-A7 and DA1-DA2 were tested in accordance with GB/T 16783.1-2006 Oil and Gas Industry Drilling Fluid Field Test Part 1 : Measured by the method described in water-based drilling fluids.

The method for measuring the recovery rate of hot rolling includes: taking 300 mL of the above drilling fluid into a high-temperature tank, then adding 50 g of 6-10 mesh interval mud shale cuttings into it, performing hot rolling at 130 ° C for 16 hours, and then adding Pass through a 40-mesh sieve, rinse with tap water for about 2 minutes, put the sieve residue at 105 ± 3 ° C for drying to constant weight, then weigh and calculate the thermal rolling recovery rate R = mass after drying / before experiment of dry weight. The larger the recovery rate, the stronger the inhibitory property of the treatment agent, and vice versa.

The measurement results are shown in Table 5.

table 5

From the results in Table 5, it can be seen that the drilling fluid prepared with the inhibitor of the present invention has more excellent inhibitory performance, wherein the drilling fluid A1 with PGA-1 inhibitor added has the highest hot rolling recovery rate, while the drilling fluid system has Better viscosity and filtration loss indicate that the inhibitor has little effect on the drilling fluid system and has good compatibility.

The preferred embodiments of the present invention have been described above in detail, however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solutions of the present invention, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in the present invention. All belong to the protection scope of the present invention.

Claims (16)

1. A shale inhibitor, characterized in that the shale inhibitor is composed of a structural unit represented by formula (1) and a structural unit represented by formula (2), Formula 1)

Formula (2)

Wherein, the molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) is 0.1-3:1; and the weight average molecular weight of the shale inhibitor is 2000-15000 g/mol. 2. The shale inhibitor according to claim 1, wherein the weight average molecular weight of the shale inhibitor is 4000-8000 g/mol. 3. The shale inhibitor according to claim 1 or 2, wherein the molecular weight distribution index Mw/Mn of the shale inhibitor is 1.5-11.6. 4. A preparation method of a shale inhibitor, characterized in that the method comprises: in the presence of an alkaline compound, carrying out an amidation reaction with glycine and arginine; the molar ratio of the glycine and arginine is: 0.1-6:1; the amidation reaction conditions are such that the weight-average molecular weight of the obtained polymer is 2000-15000 g/mol. 5. The preparation method according to claim 4, wherein the basic compound is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide. 6. The preparation method according to claim 5, wherein the basic compound is sodium hydroxide. 7. The preparation method according to claim 4, wherein the molar ratio of the basic compound to the total amount of glycine and arginine is 0.1-0.3:1. 8. The preparation method according to claim 7, wherein the molar ratio of the basic compound to the total amount of glycine and arginine is 0.15-0.25:1. 9. The preparation method according to claim 4, wherein the molar ratio of the glycine and arginine is 0.1-3:1. 10. The preparation method according to claim 4, wherein the amidation reaction conditions are such that the weight-average molecular weight of the obtained polymer is 4000-8000 g/mol. 11. The preparation method according to claim 4, wherein the amidation reaction conditions comprise: a temperature of 180-230° C. and a time of 1-8 h. 12 . The preparation method according to claim 11 , wherein the amidation reaction conditions comprise: a temperature of 190-230° C. and a time of 2-4 h. 13 . 13. A shale inhibitor prepared by the preparation method of any one of claims 4-12. 14. A drilling fluid, characterized in that the drilling fluid contains the shale inhibitor according to any one of claims 1-3 and 13. 15. The drilling fluid according to claim 14, wherein the content of the shale inhibitor is 0.5-2 wt%. 16. The application of the drilling fluid according to claim 14 or 15 in the stabilization of shale wellbore.