CN108084984A - A kind of agent for releasing for reducing guanidine gum fracturing fluid and being injured in sandstone reservoir - Google Patents

Abstract

The invention discloses a release agent for reducing the damage of guar gum fracturing fluid in sandstone reservoirs, which consists of the following components by weight percentage: 10-22% of salt, 2-6% of softener, and 5-15% of hydrogen bond breaker %, methanol 5‑15%, and the rest is water. The salt is one of NaCl and KCl or a mixture of the two in any proportion. The softening agent is a mixture of one, two or three of coconut oil fatty acid diethanolamide, glycerol polyoxyethylene polyoxypropylene ether and fatty amine polyoxyethylene ether in any proportion. The hydrogen bond breaking agent is trimethylol (amino) methane. The invention is reliable in principle and high in use efficiency, fundamentally eliminates the force between guar gum and guar gum, and between guar gum and rock, avoids excessive use of additives in the fracturing process, reduces costs and protects the environment, and overcomes the existing The defects and deficiencies of the technology have broad market application prospects.

Description

A release agent for reducing the damage of guar gum fracturing fluid in sandstone reservoirs

technical field

The invention belongs to the field of petroleum and natural gas development, and in particular relates to a release agent capable of reducing the adsorption damage of guar gum fracturing fluid in rock reservoirs during the process of oil and natural gas production enhancement and reformation.

technical background

With the continuous advancement of oil and gas energy development, low-porosity and low-permeability reservoirs have gradually become the mainstream object of oil and gas resource exploration and development. Low-porosity and low-permeability reservoirs could not be commercially developed in the past due to cost constraints. However, with the rapid development of reservoir stimulation technologies such as hydraulic fracturing in recent years, it has provided an important guarantee for the development of such oil and gas resources.

Hydraulic fracturing is to use a combination of high-pressure pump trucks to pump fracturing fluid into the reservoir with a displacement greater than the fracture pressure of the reservoir to generate artificial fractures. Since the fracturing fluid needs to carry proppant into the reservoir to form a high-speed flow channel with a certain width and length, it needs to have a high viscosity to ensure the migration of proppant in the wellbore and fractures.

At present, due to the advantages of low cost, high efficiency, and mature technology, guar gum fracturing fluid occupies a dominant position in fracturing fluid systems at home and abroad. The main components of the guar gum fracturing fluid system include: water, guar gum, fungicide, anti-swelling agent, crosslinking agent and drainage aid, etc. The main function of guar gum is to increase the viscosity of the fracturing fluid as a thickener for the fracturing fluid system. Viscosity, to ensure the smooth progress of fracturing construction. However, a large amount of foreign fluid entering the formation will cause physical and chemical reactions between the fracturing fluid and formation fluid and rocks, resulting in formation damage. Liao Li et al. (Liao Li et al. Research on the application of ultra-low concentration guar gum fracturing fluid in Sulige gas field. Drilling and production technology, 2013, volume 36, issue 5) found that guar gum has a strong Adsorption capacity can be adsorbed on the surface of rock pores, resulting in a decrease in the radius of rock pore throats and a decrease in permeability. Xu Linjing et al. (Xu Linjing et al. Damage characteristics of guar gum fracturing fluid to reservoir permeability. Xinjiang Petroleum Geology, 2016, Volume 37, Issue 4) believed that the damage of guar gum fracturing fluid to core matrix is mainly divided into Water phase damage and guar gum adsorption and retention damage, among which guar gum adsorption and retention damage accounted for as high as 43.6%.

In recent years, some domestic scholars have carried out research on low-injury fracturing fluid systems. The invention patent "low-injury fracturing fluid system" (ZL200910091732.5) mainly reduces the concentration of thickeners in fracturing fluids and adds traditional additives. The amount is optimized to achieve the purpose of reducing reservoir damage. The invention patent "a low-damage fracturing fluid and its preparation method" (ZL201110311137.5) achieved a significant reduction in the residue rate of the guar gum fracturing fluid system by continuing to reduce the concentration of guar gum in the fracturing fluid and adding a surfactant. The invention patent "a low-harm small molecule guar gum fracturing fluid" (ZL201110263461.4) realizes the control of the damage of guar gum fracturing fluid by reducing the molecular weight of guar gum. However, the above-mentioned methods are essentially reducing the damage by reducing the amount of guar gum, and there is no real solution to the damage of guar gum in the reservoir, let alone the adsorption of guar gum on the rock wall. lifting measures.

Invention patent "A method for reducing the residue of guar gum fracturing fluid" (CN201110199310.7) Add biological enzyme gel breaker GLZ-1 into guar gum fracturing fluid, the biological enzyme gel breaker is at pH7-14, temperature 40 Break the gel within the range of -70°C, and degrade the cross-linked guar gum into a gel-breaking fluid containing polysaccharides, monosaccharides and residues; the dosage of the biological enzyme gel breaker is 0.1-0.5% of the weight of the guar gum fracturing fluid; Gram-negative bacillus BH-21 is added to the gel-breaking solution, and the microbial gram-negative bacillus BH-21 takes the biological enzyme gel-breaking solution as a nutrient source, and ferments at 40-70°C for 24-48h, and the gel-breaking solution and The residue is converted into small molecular substances to further degrade the undegraded residue of the biological enzyme; the amount of residue of the gel-breaking solution treated with the high-efficiency biological enzyme gel-breaking solution fermented for 48 hours by microorganism BH-21 is higher than that of the high-efficiency biological enzyme breaking gel without microbial treatment The amount of liquid residue was reduced by 50%, which reduced the damage of guar gum residue and residue to the reservoir to a certain extent, but did not eliminate it.

Based on the full understanding of the interaction between guar gum and rocks, the present invention selects suitable chemical agents to reduce or release the force between guar gum and rocks, so that guar gum cannot interact with rocks and will not stay in the pores, and can The fluid flows out of the formation, thus reducing the plugging effect of guar gum on the rock from the root.

Contents of the invention

The purpose of the present invention is to provide a release agent that reduces the damage of guar gum fracturing fluid in sandstone reservoirs. The force between them can avoid excessive use of additives in the fracturing process, reduce costs and protect the environment, overcome the defects and deficiencies of the existing technology, and have broad market application prospects.

In order to achieve the above technical objectives, the present invention provides the following technical solutions.

The force between guar gum and sandstone is mainly electrostatic force, van der Waals force and hydrogen bond. The release agent provided by the invention can effectively reduce these three forces, thereby reducing the damage of guar gum to the reservoir and improving the effect of reconstruction.

A release agent for reducing the damage of guar gum fracturing fluid in sandstone reservoirs, consisting of the following components by weight percentage: 10-22% of salt, 2-6% of softener, 5-15% of hydrogen bond breaker, and 5% of methanol -15%, the rest is water.

The salt is one of NaCl and KCl or a mixture of the two in any proportion.

The softening agent is a mixture of one, two or three of coconut oil fatty acid diethanolamide, glycerol polyoxyethylene polyoxypropylene ether, and fatty amine polyoxyethylene ether.

The hydrogen bond breaking agent is trimethylol (amino) methane.

After the guar gum fracturing fluid is injected into the formation, the molecular chains of the guar gum are broken by the action of the gel breaker, and become molecular fragments with a molecular weight ranging from hundreds of thousands to tens of thousands. These fragments still retain the mannose and semi The structural characteristics of the lactose chain, and the sugar chain contains a large number of hydroxyl groups, the hydroxyl groups and the hydroxyl groups and the rock will act through non-covalent electrostatic forces, van der Waals forces, hydrogen bonds, etc., resulting in sugar The chains are intertwined into clusters or adsorbed on the rock surface, blocking the pores of the rock and seriously restricting the flow of formation fluid, so that the production capacity after fracturing cannot meet expectations. The present invention adopts targeted chemical agents to reduce or eliminate the non-covalent bond between the hydroxyl groups on the molecular chain of guar gum or the non-covalent bond with the rock from the mechanism, so as to prevent the guar gum from agglomerating in the pores or being adsorbed on the rock surface. In the present invention, the salt can interact with the guar gum molecule through the form of a coordination bond, so that the guar gum chain in the system is charged, effectively weakening the electrostatic interaction between the guar gum molecular chains; the softening agent can extend the guar gum molecular chain to avoid It forms agglomerates, and at the same time can change the surface of the rock to be oil-wet, weaken the hydrophilic hydroxyl on the guar gum and the rock to generate hydrogen bonds; the hydrogen bond breaker will destroy the hydrogen bond formed between the guar gum and the rock, and reduce the maximum amount of guanidine The hydrogen bond between the gum and the rock reduces the amount of adsorption, and at the same time destroys the hydrogen bond between the guar gum molecules and within the molecule, preventing the guar gum from forming into agglomerates and blocking the pores of the rock.

Compared with the prior art, the present invention is based on the accurate understanding of the force of the guar gum molecules in the aqueous solution and the interaction between the guar gum molecules and the rock, and adopts suitable chemical agents to relieve these forces. Existing methods to reduce the damage of fracturing fluid to the formation are only to generally deal with the retention of fracturing fluid in the rock, increase the amount of breaker, and reduce the molecular weight of guar gum even lower. However, these methods only reduce the capillary force of water in the tiny pores according to the traditional means. With the reduction of the pores, the capillary force will increase rapidly, and the simple latex drainage aid has been unable to play an effective role. The method of increasing the gel breaker will affect the performance of the fracturing fluid, and the gel breaker cannot completely destroy the guar gum molecular chain under the formation conditions, and there will be some large molecular guar gum molecules remaining. It is very easy to block the passage of oil and gas in groups in the pore roar of the formation. However, the present invention fundamentally eliminates the force between guar gum and guar gum, and between guar gum and rock, avoids excessive use of additives in the fracturing process, reduces costs and protects the environment.

Description of drawings

Fig. 1 is the permeability recovery curve of the tight core after use in Example 1.

Fig. 2 is the permeability recovery curve of the tight core after use in Example 4.

specific embodiment

The present invention is further illustrated below by means of the accompanying drawings and examples.

Example 1

Add 57kg of water into the reaction kettle, add 10kg of NaCl and 15kg of trimethylol (amino)methane under stirring, add 15kg of methanol after stirring evenly, and finally add 3kg of coconut oil fatty acid diethanolamide, mix evenly and discharge.

Example 2

Add 57kg of water into the reaction kettle, add 12kgNaCl and 10kgKCl, 8kg of trimethylol (amino)methane under stirring, add 9kg of methanol after stirring evenly, and finally add 2kg of coconut oil fatty acid diethanolamide and 2kg of glycerol polyoxyethylene poly Oxypropylene ether, mix evenly and discharge.

Example 3

Add 60kg of water to the reaction kettle, add 22kg of KCl and 5kg of trimethylol (amino)methane under stirring, add 7kg of methanol after stirring evenly, and finally add 3kg of fatty amine polyoxyethylene ether and 3kg of glycerol polyoxyethylene polyoxypropylene Ether, mixed evenly and discharged.

Example 4

Add 52kg of water into the reaction kettle, add 16kg of KCl and 15kg of trimethylol (amino)methane under stirring, add 15kg of methanol after stirring evenly, and finally add 2kg of glycerol polyoxyethylene polyoxypropylene ether, mix well and discharge.

Example 5

Add 66kg of water into the reaction kettle, add 15kg of NaCl and 9kg of trimethylol (amino)methane under stirring, add 5kg of methanol after stirring well, and finally add 2kg of coconut oil fatty acid diethanolamide and 3kg of fatty amine polyoxyethylene ether, and mix well After discharge.

The release agent prepared in Example 1 and Example 4 was used in the tight sandstone of the western Sichuan reservoir to test the effect, and the results are shown in Fig. 1 and Fig. 2 .

As can be seen from the figure, after the release agent was added, the permeability of the core damaged by the fracturing fluid was increased by more than 50% than the permeability after the damage, indicating that the release agent for reducing the damage of guar gum fracturing fluid in the present invention can effectively reduce the guanidine The glue can damage the reservoir and increase the permeability of the formation after pressure.

Claims (4)

1. A release agent that reduces the damage of guar gum fracturing fluid in sandstone reservoir formations, consisting of the following components by weight percentage: 10-22% of salt, 2-6% of softening agent, 5-15% of hydrogen bond breaker, Methanol 5-15%, the rest is water. 2. a kind of release agent that reduces the harm of guar gum fracturing fluid in sandstone reservoir formation as claimed in claim 1, is characterized in that, described salt is one or two arbitrary ratio mixtures in NaCl, KCl. 3. a kind of release agent that reduces guar gum fracturing fluid damage in sandstone reservoir as claimed in claim 1, is characterized in that, described softening agent is coconut oil fatty acid diethanol amide, glycerol polyoxyethylene polyoxygen A mixture of one, two or three of propylene ether and aliphatic amine polyoxyethylene ether in any proportion. 4. a kind of release agent that reduces guar gum fracturing fluid damage in sandstone reservoir as claimed in claim 1, is characterized in that, described hydrogen bond breaking agent is trimethylol (amino) methane.