阅读说明：本技术 一种可增强钻井液封堵性能的封堵剂及其封堵方法和应用 (Plugging agent capable of enhancing drilling fluid plugging performance and plugging method and application thereof ) 是由 王京光 *** 赵海锋 丁磊 寄晓宁 郭康 *** 赵雷 王勇强 张长庚 贾俊 于 2020-06-12 设计创作，主要内容包括：本发明公开了一种可增强钻井液封堵性能的封堵剂及其封堵方法和应用,包括以下步骤：步骤1)针对钻井地层裂缝情况选择两种不同类型的封堵剂,其中一种封堵剂为惰性颗粒,另一种封堵剂为可变形聚合物；步骤2)将两种不同类型的封堵剂添加到钻井液中,其中惰性颗粒的添加量为钻井液的2.0％～4.0％,其中可变形聚合物的添加量为钻井液的1.0％～3.0％；步骤3)将添加了两种不同类型封堵剂的钻井液泵人钻井中,钻井液中的惰性颗粒可以迅速进入地层裂缝架桥形成内封堵层；所述可变形聚合物在惰性颗粒形成的内封堵层基础上进行微交联可变形封堵,形成外封堵层。(The invention discloses a plugging agent capable of enhancing the plugging performance of drilling fluid, and a plugging method and application thereof, wherein the plugging agent comprises the following steps: step 1) selecting two different types of plugging agents according to the condition of a well drilling stratum fracture, wherein one of the plugging agents is inert particles, and the other plugging agent is a deformable polymer; step 2) adding two different types of plugging agents into the drilling fluid, wherein the addition amount of the inert particles is 2.0-4.0% of the drilling fluid, and the addition amount of the deformable polymer is 1.0-3.0% of the drilling fluid; step 3) pumping the drilling fluid added with two different types of plugging agents into a human drilling well, wherein inert particles in the drilling fluid can rapidly enter a stratum fracture bridge to form an inner plugging layer; the deformable polymer is subjected to micro-crosslinking deformable plugging on the basis of an inner plugging layer formed by inert particles to form an outer plugging layer.)

1. A plugging method capable of enhancing drilling fluid plugging performance is characterized by comprising the following steps:

step 1) selecting two different types of plugging agents according to the condition of a well drilling stratum fracture, wherein one of the plugging agents is inert particles, and the other plugging agent is a deformable polymer;

step 2) adding two different types of plugging agents into the drilling fluid, wherein the addition amount of the inert particles is 2.0-4.0% of the drilling fluid, and the addition amount of the deformable polymer is 1.0-3.0% of the drilling fluid;

step 3) pumping the drilling fluid added with two different types of plugging agents into a human drilling well, wherein inert particles in the drilling fluid can rapidly enter a stratum fracture bridge to form an inner plugging layer; the deformable polymer is subjected to micro-crosslinking deformable plugging on the basis of an inner plugging layer formed by inert particles to form an outer plugging layer.

2. The plugging method capable of enhancing the plugging performance of the drilling fluid according to claim 1, wherein the plugging method comprises the following steps: the stratum cracks in the step 1) comprise nano-scale microcracks, 1-100 um micron-scale microcracks, 100-500 um microcracks or micropores, 500-1000 um microcracks and middle-upper stratum microcracks.

3. The plugging method capable of enhancing the plugging performance of the drilling fluid according to claim 2, wherein the plugging method comprises the following steps: when the drilling stratum is a nano-scale micro-crack or a nano-micron micro-crack, the selected inert particles are nano inert particles G314 or nano inert particles G314-2, and the selected deformable polymer is a micro-crosslinking nano polymer plugging agent G308 or a micro-crosslinking nano polymer plugging agent G332; when the drilling stratum is a micron-sized micro crack of 1-100 um, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is a micro-crosslinked nano polymer plugging agent G308 or a micro-crosslinked nano polymer plugging agent G332; when the drilling stratum is 100-500 um microcracks or micropores, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is emulsified paraffin G325; when the drilling stratum is a micro crack of 500-1000 um, the inert particles are 800-mesh limestone powder, and the deformable polymer is emulsified paraffin G325; when the drilling stratum is a middle-upper stratum microcrack, the selected inert particles are 400-mesh or 600-mesh limestone powder, and the selected deformable polymer is emulsified paraffin G325.

4. The plugging method capable of enhancing the plugging performance of the drilling fluid according to claim 3, wherein the plugging method comprises the following steps: when the drilling stratum is a nano-scale micro-crack or a nano-micron micro-crack and the drilling fluid is water-based drilling fluid, the selected inert particles are nano inert particles G314, and the selected deformable polymer is a micro-crosslinked nano polymer plugging agent G308; when the drilling stratum is a nano-scale micro-fracture or a nano-micron micro-fracture and the drilling fluid is oil-based drilling fluid, the selected inert particles are nano inert particles G314-2, and the selected deformable polymer is a micro-crosslinked nano polymer plugging agent G332; when the drilling stratum is a micron-sized micro-crack of 1-100 mu m and the drilling fluid is water-based drilling fluid, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is a micro-crosslinked nano-polymer plugging agent G308; when the drilling stratum is a micron-sized micro-crack of 1-100 microns and the drilling fluid is an oil-based drilling fluid, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is a micro-crosslinked nano-polymer plugging agent G332.

5. The plugging method capable of enhancing the plugging performance of the drilling fluid according to claim 3, wherein the plugging method comprises the following steps: the inert particles have a particle size 1/3 times that of the corresponding formation fracture, wherein the particle size of the deformable polymer is 2/3 times greater than the corresponding formation fracture, and the particle size of the deformable polymer is more than 3 times that of the corresponding formation fracture when crosslinked.

6. The plugging method capable of enhancing the plugging performance of the drilling fluid according to claim 1, wherein the method for calculating the instantaneous fluid loss of the drilling fluid by using two different types of plugging agents in the step 1) comprises the following steps:

V₀＝4V_7.5-2V₃₀

in the formula:

V₀-high temperature high pressure instantaneous fluid loss, mL;

V_7.5high temperature and high pressure filtration loss of 7.5min, mL;

V₃₀high temperature high pressure filtration loss, mL, for 30 min.

7. The plugging method capable of enhancing the plugging performance of the drilling fluid according to claim 6, wherein the calculation method of the instantaneous fluid loss reduction rate of the two different types of plugging agents in the step 1) for the drilling fluid is as follows:

in the formula:

r-reduction of instantaneous fluid loss,%;

V₁the high-temperature high-pressure instantaneous filtration loss (mL) of the drilling fluid added with two different types of plugging agents;

V₀high temperature and high pressure instantaneous fluid loss of drilling fluid, mL.

8. A plugging agent capable of enhancing the plugging performance of drilling fluid is characterized in that: the two different types of plugging agents of any one of claims 1 to 7, wherein one of the plugging agents is inert particles and the other plugging agent is a deformable polymer, the inert particles are added in an amount of 2.0% to 4.0% of the drilling fluid, and the deformable polymer is added in an amount of 1.0% to 3.0% of the drilling fluid.

9. The use of a plugging agent according to claim 8 for enhancing the plugging properties of a drilling fluid, wherein: the plugging agent capable of enhancing the plugging property of the drilling fluid can be used for water-based drilling fluid and oil-based drilling fluid, and is suitable for drilling construction of shale gas horizontal wells, shale oil horizontal wells or carbonaceous mudstone horizontal wells with higher requirements on the plugging and anti-collapse properties of the drilling fluid.

Technical Field

The invention belongs to the technical field of drilling fluid performance enhancement, and particularly relates to a plugging agent capable of enhancing the plugging performance of a drilling fluid, a plugging method and application thereof, which can be applied to a water-based drilling fluid and an oil-based drilling fluid, and are suitable for drilling construction with higher requirements on the plugging and anti-collapse performance of the drilling fluid in shale gas horizontal wells, shale oil horizontal wells or carbonaceous mudstone horizontal wells.

Background

Along with the large-scale development of unconventional gas reservoirs marked by shale gas at home and abroad, the oil-based drilling fluid is more and more widely applied. Compared with the traditional water-based drilling fluid, the oil-based drilling fluid is widely applied to shale gas drilling because of good inhibition performance, lubricating performance and rheological performance.

However, the oil-based drilling fluid generally has the problems of heavy pollution, difficult treatment of oil-based drilling cuttings and high use cost of the oil-based drilling fluid. Compared with oil-based drilling fluid, the water-based drilling fluid has the advantages of low pollution, low cost and the like. Shale gas horizontal wells can adopt oil-based drilling fluids and synthetic-based drilling fluids, and can also adopt strongly-inhibitive water-based drilling fluids, and the key points of the shale gas horizontal wells are to ensure the stability, lubrication, anti-seizing and well cleaning of well walls.

Compared with oil-based drilling fluid, the anti-collapse performance of the water-based drilling fluid is weaker. When the anti-collapse agent is applied to shale gas horizontal wells, the anti-collapse performance of the water-based drilling fluid must be greatly enhanced. For water-based drilling fluids, the key to ensuring the stability of the well wall is to provide good plugging capability. It is desirable that drilling fluids be able to block the micro-porosity between the shale mineral particles to prevent the infiltration of filtrate leading to the creation of secondary micro-cracks while maintaining as low a fluid loss as possible. The shale pores in China are mostly in the nanometer level, the particle size of the conventional plugging agent is large and far larger than that of the shale, the micro pores and micro cracks are difficult to plug, filtrate enters the stratum, and therefore well wall instability is caused, and meanwhile, a nano-micron plugging evaluation method is lacked. The shale microcracks develop, filtrate enters along the microcracks to cause borehole wall instability, the size of the shale microcracks is nm-mum grade, and the existing fluid loss media are basically above mum grade, such as PPA sand discs (minimum 3μm) and HTHP filter paper (20μm).

In the past, the problem of borehole wall instability in the shale gas horizontal well construction process is usually firstly adopted to improve the density of drilling fluid. The drilling fluid with higher density can more easily invade stratum micropores and microcracks, and secondary microcracks are added into the stratum to cause the stripping, collapse and instability of well walls. When the plugging capacity of the drilling fluid is insufficient, a vicious circle of 'borehole wall instability → density improvement → transient stability → aggravation of filtrate invasion → collapse deterioration' is easy to occur, the higher the field density is, the worse the borehole wall stability is, the more prominent the borehole wall block falling and the difficult problem of drill sticking are.

In the existing method, a plurality of plugging agents are added and are mixed together to plug according to different particle sizes of the plugging agents, only the particle size of the plugging agents is concerned, the plugging agents are accumulated according to plugging substances, the formed plugging layer is lack of research, the level of the formed plugging layer is not researched, the field plugging is guided according to the previous theory, and the plugging effect is poor.

Therefore, research on a nano-micro fracture anti-collapse evaluation method is urgently needed, and a plugging agent formula for a water-based drilling fluid, which has a good plugging effect, particularly has an excellent plugging agent for pores and micro fractures, has a good anti-collapse effect for easily collapsed strata such as shale and carbonaceous mudstone, can remarkably enhance the plugging performance of the water-based drilling fluid, and meets the requirements of shale gas horizontal wells, carbonaceous mudstone horizontal wells and horizontal wells drilled in other easily collapsed strata.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a plugging agent capable of enhancing the plugging performance of drilling fluid, a plugging method and application thereof, and overcomes the defects of the prior art that 1: the existing plugging agent has larger size, the shale pores in China are mostly in nanometer level, the particle size of the conventional plugging agent is larger and far larger than the pore size of the shale, and the micro pores and micro cracks are difficult to plug, so that filtrate enters the stratum and the well wall is unstable; 2: by adopting the method for improving the density of the drilling fluid, the drilling fluid with higher density can more easily invade stratum micropores and microcracks, and the generation of stratum secondary microcracks is added, so that the well wall is peeled off and collapsed; 3: in the prior art, a plurality of plugging agents are added and are mixed together to plug according to different particle sizes of the plugging agents, only the particle size of the plugging agents is concerned, the plugging agents are accumulated according to plugging substances, the formed plugging layer is lack of research, the level of the formed plugging layer is not researched, the field plugging is guided according to the previous theory, and the plugging effect is poor.

In order to solve the technical problem, the technical scheme of the invention is as follows: a plugging method capable of enhancing the plugging performance of drilling fluid comprises the following steps:

step 1) selecting two different types of plugging agents according to the condition of a well drilling stratum fracture, wherein one of the plugging agents is inert particles, and the other plugging agent is a deformable polymer;

step 2) adding two different types of plugging agents into the drilling fluid, wherein the addition amount of the inert particles is 2.0-4.0% of the drilling fluid, and the addition amount of the deformable polymer is 1.0-3.0% of the drilling fluid;

step 3) pumping the drilling fluid added with two different types of plugging agents into a human drilling well, wherein inert particles in the drilling fluid can rapidly enter a stratum fracture bridge to form an inner plugging layer; the deformable polymer is subjected to micro-crosslinking deformable plugging on the basis of an inner plugging layer formed by inert particles to form an outer plugging layer.

Preferably, the stratum cracks in the step 1) comprise nanometer-scale microcracks, 1-100 um micron-scale microcracks, 100-500 um microcracks or micropores, 500-1000 um microcracks and middle-upper stratum microcracks.

Preferably, when the drilling stratum is a nano-scale micro-crack or a nano-micron micro-crack, the selected inert particles are nano inert particles G314 or nano inert particles G314-2, and the selected deformable polymer is a micro-crosslinking nano polymer plugging agent G308 or a micro-crosslinking nano polymer plugging agent G332; when the drilling stratum is a micron-sized micro crack of 1-100 um, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is a micro-crosslinked nano polymer plugging agent G308 or a micro-crosslinked nano polymer plugging agent G332; when the drilling stratum is 100-500 um microcracks or micropores, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is emulsified paraffin G325; when the drilling stratum is a micro crack of 500-1000 um, the inert particles are 800-mesh limestone powder, and the deformable polymer is emulsified paraffin G325; when the drilling stratum is a middle-upper stratum microcrack, the selected inert particles are 400-mesh or 600-mesh limestone powder, and the selected deformable polymer is emulsified paraffin G325.

Preferably, when the drilling stratum is a nano-scale micro-crack or a nano-micron-scale micro-crack and the drilling fluid is water-based drilling fluid, the selected inert particles are nano inert particles G314, and the selected deformable polymer is a micro-crosslinked nano polymer plugging agent G308; when the drilling stratum is a nano-scale micro-fracture or a nano-micron micro-fracture and the drilling fluid is oil-based drilling fluid, the selected inert particles are nano inert particles G314-2, and the selected deformable polymer is a micro-crosslinked nano polymer plugging agent G332; when the drilling stratum is a micron-sized micro-crack of 1-100 mu m and the drilling fluid is water-based drilling fluid, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is a micro-crosslinked nano-polymer plugging agent G308; when the drilling stratum is a micron-sized micro-crack of 1-100 microns and the drilling fluid is an oil-based drilling fluid, the selected inert particles are 2500-mesh ultrafine calcium carbonate, and the selected deformable polymer is a micro-crosslinked nano-polymer plugging agent G332.

Preferably, the inert particles have a particle size 1/3 times that of the corresponding formation fracture, wherein the deformable polymer has a particle size 2/3 times greater than the corresponding formation fracture, and wherein the particle size is more than 3 times that of the corresponding formation fracture when the deformable polymer is crosslinked.

Preferably, the method for calculating the instantaneous fluid loss of the drilling fluid by using two different types of plugging agents in the step 1) comprises the following steps:

V₀＝4V_7.5-2V₃₀

in the formula:

V₀-high temperature high pressure instantaneous fluid loss, mL;

V_7.5high temperature and high pressure filtration loss of 7.5min, mL;

V₃₀high temperature high pressure filtration loss, mL, for 30 min.

Preferably, the method for calculating the instantaneous fluid loss reduction rate of the drilling fluid by using two different types of plugging agents in the step 1) comprises the following steps:

in the formula:

r-reduction of instantaneous fluid loss,%;

V₁the high-temperature high-pressure instantaneous filtration loss (mL) of the drilling fluid added with two different types of plugging agents;

V₀high temperature and high pressure instantaneous fluid loss of drilling fluid, mL.

Preferably, the blocking agent capable of enhancing the blocking performance of the drilling fluid comprises two different types of blocking agents as described in any one of the above, wherein one of the blocking agents is inert particles, and the other blocking agent is a deformable polymer, the addition amount of the inert particles is 2.0% -4.0% of the drilling fluid, and the addition amount of the deformable polymer is 1.0% -3.0% of the drilling fluid.

Preferably, the plugging agent capable of enhancing the plugging property of the drilling fluid can be applied to water-based drilling fluids and oil-based drilling fluids, and is suitable for drilling construction of shale gas horizontal wells, shale oil horizontal wells or carbonaceous mudstone horizontal wells with higher requirements on the plugging and anti-collapse properties of the drilling fluid.

Compared with the prior art, the invention has the advantages that:

(1) according to the invention, different types of plugging agents are selected, wherein one plugging agent is inert particles, the other plugging agent is a deformable polymer, the inert particles in the drilling fluid can rapidly enter a stratum fracture bridge to form an inner plugging layer, the invasion of filtrate into a rock stratum is rapidly reduced, and the deformable polymer is subjected to micro-crosslinking deformable plugging on the basis of the inner plugging layer formed by the inert particles to form an outer plugging layer, so that the plugging strength is enhanced, and the plugging effect is enhanced; two different plugging layers can be realized through the action time difference of the inert particles and the deformable polymer, the inert particles form an inner plugging layer by virtue of a stacking effect, the plugging effect is quick, the plugging effect is mainly a physical effect, the deformable polymer forms an outer plugging layer by virtue of crosslinking, the time is long, but the plugging strength is high, and the chemical effect is mainly a chemical effect; the invention obviously improves the plugging performance of the drilling fluid, particularly the plugging performance on microcracks and microporosities, and reduces the permeability of a plugging layer, thereby improving the anti-collapse performance of the drilling fluid, solving the problem of borehole wall instability of a shale gas horizontal well with microcrack development encountered in shale gas exploration and development at present, and meeting the requirement of safe and rapid drilling of the shale gas horizontal well;

(2) the invention has simple operation and quick effect, does not need to adjust the formula of a drilling fluid system, only needs to select proper inert particles and deformable polymers according to the condition of the cracks of the drilled stratum, and directly adds quantitative plugging agents on the basis of the original drilling fluid system, has good plugging effect, particularly has excellent plugging performance on micro-pores and micro-cracks, can obviously enhance the plugging performance of the water-based drilling fluid, and meets the requirements of shale gas horizontal wells, carbonaceous mudstone horizontal wells and horizontal wells drilled in other easily collapsed stratums;

(3) the invention does not need to obviously increase the density of the oil-based drilling fluid, reduces the occurrence probability of well leakage, and avoids vicious circle of borehole wall instability → density improvement → transient stability → aggravation of filtrate invasion → collapse deterioration.

Drawings

FIG. 1 is a graph comparing the plugging performance of sample slurries of example 6 of the present invention with a base slurry;

FIG. 2 is a graph comparing the plugging performance of sample slurries of example 7 of the present invention with a base slurry;

FIG. 3 is a graph comparing the plugging performance of sample slurries of example 8 of the present invention with a base slurry;

FIG. 4 is a graph comparing the plugging performance of the sample slurries of example 9 of the present invention with the base slurries:

FIG. 5 is a diagram illustrating a process for forming an inner blocking layer according to the present invention;

fig. 6 is a diagram illustrating a process of forming an outer blocking layer according to the present invention.

Description of reference numerals:

1-inner plugging layer, 2-outer plugging layer and 3-stratum fracture.

Detailed Description

The following describes embodiments of the present invention with reference to examples:

it should be noted that the structures, proportions, sizes, and other embodiments disclosed herein are illustrative only and are not intended to limit the scope of the invention, which is defined by the claims, since the scope of the invention is not limited by the specific structures, proportions, and dimensions, or otherwise, unless otherwise specified, since various modifications, changes in the proportions and variations thereof, can be made by those skilled in the art without departing from the spirit and scope of the invention.

In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.