CN105733528B - A kind of drilling shale low-density fluorescence drilling fluid - Google Patents

Abstract

The invention relates to a low-density fluorescent drilling fluid used for drilling shale for shale gas development. It can overcome wellbore instability and inhibit the hydration and collapse of shale formations. The technical solution is to prepare the components and contents of the raw materials used in the drilling fluid, and the mass unit is gram: sodium carbonate 1.5-2.5; bentonite 30-50 for drilling fluid; cutting agent PAC-141 10-20; drilling fluid Coating agent FBY‑502‑4; anti-high temperature and anti-salt fluid loss reducer WSG‑099 10‑20; viscosity reducer JN‑1Z 0.3‑0.8 for drilling fluid; high-gloss calcium carbonate BZ‑350030‑50; lubrication for drilling fluid agent SYP‑2 10‑20; anti-collapse plugging agent FDT‑150 30‑50 for drilling fluid; emulsified paraffin JLRP‑4020‑30; tap water 900‑1000; use 40% lye to adjust the pH of the system to 8.5, add heavy Adjust the density of the spar to 1.20g/cm ³ to obtain the drilling fluid. The drilling fluid system has little environmental pollution, good rheology, low fluorescence, and strong ability to inhibit plugging, and is used for shale drilling.

Description

A kind of low-density fluorescent drilling fluid for drilling shale

technical field

The invention relates to a low-density fluorescent drilling fluid for drilling shale used for shale gas development, which is particularly suitable for drilling long horizontal well sections of shale with developed micro-fractures.

Background technique

At present, oil-based drilling fluids are commonly used in shale gas wells at home and abroad. Because oil-based drilling fluids can increase the capillary pressure of water-wet shale and prevent drilling fluids from invading shale, oil-based drilling fluids and synthetic-based drilling fluids can be used. Effectively solve the problem of well wall instability. In dealing with the wellbore stability of shale gas horizontal wells, the use of oil-based drilling fluid system is currently the most effective measure abroad. But even if oil-based drilling fluid is used, for shale formations with developed fractures or beddings, it is necessary to strengthen the plugging to reduce the pressure transmission caused by the liquid entering the formation (blocking fluid channels). Oil-based drilling fluids have incomparable advantages over water-based drilling fluids in terms of lubrication, anti-seizure and drag reduction, and can avoid dragging problems during sliding drilling, which is the fundamental reason for their wide application. However, the oil-based working fluid changes the wettability of the low-permeability oil layer and gas layer and causes damage, which greatly reduces the permeability of the reservoir, thereby reducing the production of the oil well. Indoor core experiments show that when the core changes from hydrophilic to oil-wet, the recovery factor decreases from 51% to 17%. Therefore, oil-based drilling fluid should be used cautiously in low-permeability oil layers to drill production layers, especially when there are emulsifiers and surfactants in the oil-based drilling fluid.

Advantages and disadvantages of water-based drilling fluid compared with oil-based drilling fluid: ① environmental protection; Well wall stability is poor; ② relatively poor thermal stability, easy to gel at high temperature; ③ poor anti-pollution (solid phase and CO ₂ , H ₂ S gas pollution), heavy maintenance and processing workload; ④ insufficient lubrication and anti-seize ability. Therefore, developing a new type of water-based drilling fluid suitable for shale formations to replace oil-based drilling fluids, which can solve the problems of wellbore stability and reservoir pollution, is the key technology for shale gas drilling at present, and it is also a key technology for shale drilling at home and abroad. where the difficulty lies.

Contents of the invention

The purpose of the present invention is: in order to overcome the problem of wellbore instability when using water-based drilling fluid to drill into shale formations, suppress the hydration and collapse of shale formations, and effectively plug the micro-nano pores and fractures of shale formations. A low-density fluorescent drilling fluid for drilling shale.

In order to achieve the above object, the present invention adopts the following technical solutions: a low-density fluorescent drilling fluid for drilling into shale, characterized in that the composition and content of the raw materials used to prepare the drilling fluid are, wherein the mass unit is gram:

The pH value of the system was adjusted to 8.5 with 40% NaOH solution by mass percent; the density of the drilling fluid was adjusted to 1.20 g/cm ³ with barite.

A kind of preparation method of low-density fluorescent drilling fluid for drilling into shale of the present invention is:

First measure 1000 grams of tap water and raise the water temperature to 70°C, add 30-50 grams of bentonite for drilling fluid under low-speed 500r/min electric stirring, stir for 10 minutes, add 1.5-2.5 grams of Na ₂ CO ₃ and stir for 30 minutes, Pre-hydration at normal temperature and pressure for 24 hours; then add 10-20 grams of cutting agent PAC-141 under high-speed 8000r/min electric stirring and stir for 6 minutes, add 2-4 grams of drilling fluid with low-speed electric stirring at 500r/min for coating Stir for 5 minutes with agent FBY-50, add 10-20 grams of anti-high temperature and anti-salt fluid loss reducer WSG-099 and stir for 5 minutes, add 0.3-0.8 grams of drilling fluid viscosity reducer JN-1Z and stir for 5 minutes; then add 30-50 grams of high-gloss Calcium carbonate BZ-3500 and stir for 15 minutes, add 10-20 grams of drilling fluid with lubricant SYP-2 and stir for 5 minutes, add 30-50 grams of drilling fluid with anti-slump plugging agent FDT-150 and stir for 5 minutes, add 20-30 grams of emulsified paraffin JLRP-40 was stirred for 10 minutes; finally, NaOH was added with water to make 40% lye, and the pH of the system was adjusted to 8.5. After stirring for 30 minutes, add barite to adjust the drilling fluid density to 1.20 g/cm ³ and stir for 1 hour to obtain the low-density fluorescent drilling fluid.

Bentonite for drilling fluid used in the above preparation method, Na ₂ CO ₃ , cutting agent PAC-141, coating agent for drilling fluid FBY-50, high temperature and salt resistance fluid loss reducer WSG-099, viscosity reducer for drilling fluid JN -1Z, high-gloss calcium carbonate BZ-3500, lubricant SYP-2 for drilling fluid, anti-slump plugging agent FDT-150 for drilling fluid, emulsified paraffin JLRP-40, and barite are all products on the market. According to the industry standard or enterprise standard inspection, only those who pass the test can be used. See Table 1 for details.

Table 1 List of basic raw materials of this low-density fluorescent drilling fluid

Compared with the currently used shale drilling fluid system, the low-density water-based drilling fluid for drilling shale provided by the present invention has the following beneficial effects: ① Compared with oil-based drilling fluid, this drilling fluid has less environmental pollution; Strong ability to inhibit plugging; ③ can effectively reduce the collapse pressure; ④ fluorescent material can track the drilling process at any time; ⑤ relatively low cost; ⑥ easy to deal with lost circulation, etc.

Detailed ways:

Below in conjunction with specific example the present invention will be further described

Example 1: A preparation method of low-density fluorescent drilling fluid for drilling into shale.

First measure 1000 grams of tap water, raise the water temperature to 70°C, add 30 grams of bentonite for drilling fluid under electric stirring at a low speed of 500r/min, stir for 10 minutes, add 1.5 grams of Na ₂ CO ₃ and stir for another 30 minutes, and pre-heat at room temperature and pressure. After hydration for 24 hours, add 15 grams of cutting agent PAC-141 under high-speed 8000r/min electric stirring and stir for 6 minutes, then add 2 grams of drilling fluid coating agent FBY-50 and stir for 5 minutes under low-speed 500r/min electric stirring, add Stir 10 grams of anti-high temperature and anti-salt fluid loss reducer WSG-099 for 5 minutes, add 0.5 grams of drilling fluid viscosity reducer JN-1Z and stir for 5 minutes, add 40 grams of high-gloss calcium carbonate BZ-3500 and stir for 15 minutes, add 10 grams of drilling fluid for lubrication Add agent SYP-2 and stir for 5 minutes, add 40 grams of drilling fluid anti-slump plugging agent FDT-150 and stir for 5 minutes, add 25 grams of emulsified paraffin wax JLRP-40 and stir for 10 minutes, add NaOH and water to prepare 40% lye, and adjust the pH of the system to 8.5. After stirring for 30 minutes, add barite to adjust the drilling fluid density to 1.20 g/cm ³ and stir for 1 hour to obtain the low-density fluorescent drilling fluid.

Example 2: The rolling recovery rate of the drilling fluid system of the present invention was measured by using an XGRL-2 type roller heating furnace.

Table 2 Experimental results of rolling recovery rate of this low-density fluorescent drilling fluid system

Drilling Fluid Formula Experimental conditions Recovery mass (g) Recovery rate(%) Clear water + 50g red bed soil 105℃/16h 5.54 11.08 Low-density fluorescent drilling fluid system + 50g red bed soil 105℃/16h 48.32 96.64

Note: 1) The red layer soil is Sichuan red layer soil debris, and the shale outcrop is Chang 7 shale outcrop, all of which are 6-10 mesh, and the recovery rate is over 40 mesh; 2) The results in the table are all 2 times The mean of the experimental data.

Table 3 Experimental results of linear expansion of this low-density fluorescent drilling fluid system

Note: 1) The core is formed by pressing bentonite (mixed soil) for drilling fluid; 2) The filtrate is the filtrate that was extruded after the system was hot rolled at 105°C/16h; 3) The results in the table are the average of the data of two experiments.

From Table 2 and Table 3, the rolling recovery rate and linear expansion rate experiments of the low-density fluorescent drilling fluid show that the rolling recovery rate reaches more than 95%, and the 16h linear expansion rate is only 22.46%, which has good inhibition of hydration dispersion and expansion.

Example 3: The thermal stability effect of the low-density fluorescent drilling fluid was tested by using the XGRL-2 type roller heating furnace for continuous hot rolling.

Table 4 Thermal stability evaluation of this low-density fluorescent drilling fluid system

Table 5 Evaluation of temperature resistance of this low-density fluorescent drilling fluid system

From the thermal stability results in Table 4, it can be seen that the viscosity, shear and fluid loss of the system change little with the increase of rolling time, and the system has good thermal stability. From the temperature resistance test in Table 5, it can be seen that the viscosity and shear of the low-density fluorescent drilling fluid are greatly reduced at 150 °C, and the water loss of HTHP is greatly increased, but at 120 °C, the rheology can be well maintained, and the water loss of HTHP can be well maintained. , can resist temperature 120 ℃.

Claims (2)

1. a kind of drilling shale low-density fluorescence drilling fluid, it is characterized in that：It prepares the raw materials used component of the drilling fluid and contains It measures and is, mass unit is gram：

The NaOH solution regulation system pH value for being 40% with mass percentage concentration is 8.5；With barite regulating density of drilling liquid extremely 1.20g/cm³。

2. a kind of preparation method of drilling fluid as described in claim 1, it is characterized in that：1000 grams of tap water is first measured by water temperature 70 DEG C are risen to, 30-50 grams of drilling fluid bentonite is added under low speed 500r/min electric stirrings, stirs 10min, is added in 1.5-2.5 grams of Na₂CO₃It is stirred for 30min, prehydration is for 24 hours under normal temperature and pressure；It is added under high speed 8000r/min electric stirrings again 10-20 grams of extracting and cutting agent PAC-141 stirs 6min, and 2-4 grams of drilling fluid coating agent is added under low speed 500r/min electric stirrings FBY-50 stirs 5min, adds in 10-20 grams of high-temperature resisting and salt-resisting fluid loss additive WSG-099 stirring 5min, adds in 0.3-0.8 grams of drilling well Liquid stirs 5min with thinner JN-1Z；Then 30-50 grams of bloom calcium carbonate BZ-3500 stirring 15min is added in, adds in 10-20 grams Lubricant for drilling fluids SYP-2 stirs 5min, adds in 30-50 grams of drilling fluid and stirs 5min with anti-collapse sealing agent FDT-150, adds in 20-30 grams of emulsified wax JLRP-40 stirs 10min；Finally water is added to be configured to 40% lye with NaOH, regulation system pH is 8.5, barite regulating density of drilling liquid is added in 1.20g/cm after stirring 30min³This low-density fluorescence is made in stirring 1 hour Drilling fluid.