CN-121993187-A - Experimental device and method for evaluating stability of drilling fluid on scattered coal seam

CN121993187ACN 121993187 ACN121993187 ACN 121993187ACN-121993187-A

Abstract

The invention belongs to the technical field of coalbed methane exploration and development, and particularly provides an experimental device and method for evaluating stability of a drilling fluid on a scattered coal bed, wherein a rock core is prefabricated by pressing scattered coal particles; filling a prefabricated rock core between a rubber cylinder and a rock core groove, injecting liquid into the rubber cylinder to pressurize, expanding the rubber cylinder, extruding the filled prefabricated rock core to simulate the formation pressure and the drilling fluid pressure, stopping injecting liquid, contracting the rubber cylinder, taking out the rubber cylinder, injecting water into the middle part of the rock core groove by a water injection component, collecting coal dust flushed out of the rock core groove, determining the instability rate of the coal rock on the well wall, the expansion rate of the diameter of the well and the fitting degree of the particle size of the coal dust, and finishing the evaluation of the stability of the broken coal seam. The method solves the problems that the existing broken coal seam coal body structure is broken, a rock core column cannot be drilled, and the effective evaluation of the drilling fluid on the stability of the broken coal seam cannot be completed.

Inventors

ZHANG XIAOPING
ZHAO HAIFENG
WANG JINGGUANG
CHEN LEI
JIA JUN
XU CHAOYANG
SU HUAN
DING LEI
CAO HUI
GUO KANG

Assignees

中国石油天然气集团有限公司
中国石油集团川庆钻探工程有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (10)

1. An experimental device for evaluating stability of drilling fluid on a broken coal seam is characterized by comprising a water injection component, a rubber barrel (5) and a core groove (6), wherein the rubber barrel (5) is horizontally connected in a penetrating manner to the middle of the core groove (6), broken coal (7) is filled between the rubber barrel (5) and the core groove (6), and the rubber barrel (5) is connected with the water injection component.
2. The experimental device for evaluating the stability of drilling fluid to a broken coal seam according to claim 1, wherein the water injection component comprises a liquid tank (1) and a circulating pump (2), an outlet of the liquid tank (1) is connected with one end of a rubber cylinder (5) through the circulating pump (2), and the other end of the rubber cylinder (5) is connected with an inlet of the liquid tank (1).
3. The experimental device for evaluating the stability of the drilling fluid on the broken coal seam according to claim 2, wherein an inlet joint (4) is arranged in the middle of one end of the core groove (6), and one end of a rubber cylinder (5) is sleeved in the inlet joint (4).
4. The experimental device for evaluating the stability of the drilling fluid on the broken coal seam according to claim 3, wherein an outlet joint (9) is arranged in the middle of the other end of the core groove (6), and the other end of the rubber cylinder (5) is sleeved in the outlet joint (9).
5. The experimental device for evaluating the stability of the drilling fluid on the broken coal seam according to claim 4, wherein valves (3) are respectively arranged between the circulating pump (2) and the inlet joint (4) and between the outlet joint (9) and the inlet of the liquid tank (1).
6. The experimental device for evaluating the stability of the drilling fluid to the broken coal seam according to claim 1, wherein the liquid tank (1) is filled with the produced coal seam water.
7. An experimental method for evaluating stability of drilling fluid on a broken coal seam is characterized by comprising the following steps: S1, compacting a prefabricated rock core by using crushed scattered coal particles; s2, horizontally installing a rubber cylinder (5) in the middle of the core groove (6), and filling a prefabricated core between the rubber cylinder (5) and the core groove (6); s3, injecting liquid into the rubber cylinder (5) through the water injection component for pressurizing, so that the rubber cylinder (5) is expanded, and extruding a prefabricated core filled between the rubber cylinder (5) and the core groove (6) to simulate formation pressure and drilling fluid pressure; s4, stopping injecting liquid by the water injection component, contracting the rubber cylinder (5), and taking out the rubber cylinder (5); S5, injecting water into the middle of the core groove (6) through the water injection component, collecting coal dust rushing out of the core groove (6), determining the instability rate of the well wall coal and rock, the diameter expansion rate of the well shaft and the particle size fitting degree of the coal dust, and finishing the evaluation of the stability of the broken coal seam.
8. The experimental device for evaluating the stability of the drilling fluid to the broken coal seam as set forth in claim 7, wherein the greater the instability rate of the well wall coal rock in the step S5, the worse the stability of the drilling fluid to the well wall.
9. The experimental device for evaluating the stability of the drilling fluid to the broken coal seam as set forth in claim 7, wherein the greater the diameter expansion rate of the well bore in the step S5, the worse the stability of the drilling fluid to the well wall and the higher the risk of the well wall instability.
10. The experimental device for evaluating the stability of the drilling fluid to the broken coal seam as set forth in claim 7, wherein the higher the fitting degree between the particle size distribution of the coal dust and the particle size distribution of the broken coal seam in the step S5 is, the worse the stability of the drilling fluid to the well wall is.

Description

Experimental device and method for evaluating stability of drilling fluid on scattered coal seam Technical Field The invention belongs to the technical field of coal bed gas exploration and development, and particularly relates to an experimental device and method for evaluating stability of a drilling fluid on a scattered coal bed. Background The coalbed methane has huge resource quantity and wide prospect of exploration and development, and can be a necessary supplement of natural gas resources. Although the deep coal bed gas development output breaks through, the horizontal well becomes a main development technology, the engineering cost of the coal bed gas horizontal well is high, the engineering technical problem of restricting the deep coal bed gas development is still faced, wherein the stability of the wall of the coal bed horizontal section is one of important technical barriers, and is also a key for determining the success and failure of the deep coal bed gas horizontal well drilling and completion, and no more effective experimental evaluation method exists at present. The deep coal seam has a complex coal body structure and large difference, wherein the broken coal seam has larger influence on the stability of the well wall, the traditional rock mechanics coulomb criterion and the stress support theory are not suitable for well wall stability evaluation of the deep broken coal seam, the serious well wall instability can directly lead to scrapping of a horizontal well, the well cementation quality of a horizontal section of the coal seam is also influenced, and an experimental evaluation method for researching the stability of the broken coal seam to the well wall of the horizontal well of the coal seam gas is needed to be urgently researched. The traditional coal seam stability evaluation method has a plurality of limitations and disadvantages that 1, the coal seam coal body structure is assumed to be uniformly distributed, 2, the theory based on continuous media and elastoplastics is not considered, 3, the coal body structure of a rock core column must be drilled, and 4, the interface physical property and mechanical difference problem of coal rock and mudstone are not considered. The Chinese patent document with the publication number of CN115577497A discloses a method, a system and a storable medium for detecting the stability of coal and rock mass, which relate to the technical field of coal mining and comprise the steps of acquiring goaf data and establishing a three-dimensional model through a three-dimensional scanning technology; the method comprises the steps of collecting rock samples of typical coal rock, carrying out indoor rock mechanical test on a dry and water-saturated coal rock test piece to obtain basic rock mechanical parameter indexes and permeability coefficients of the coal rock, carrying out macroscopic mechanical parameter evaluation of the coal rock by adopting H-B strength criteria according to underground water conditions and indoor rock mechanical test, carrying out fluid-solid coupling calculation analysis of the coal rock by utilizing numerical simulation by combining three-dimensional morphology, water conditions, geological conditions and rock mechanical characteristics of a water-forming empty area, and obtaining an evaluation result of coal rock stability. The method can precisely detect the goaf of the coal mine, analyze the stability of the coal rock mass and provide technical guarantee and safety support for the safety production of the coal mine. The literature is used for detecting the stability of coal and rock mass, the structure of the coal and rock mass is uniformly distributed, and the literature is not suitable for detecting the stability of the coal mass of a broken coal seam. The broken coal bed coal body structure is broken, a rock core column cannot be drilled, and the performance of the drilling fluid cannot be effectively evaluated. It is needed to develop an experimental device and an evaluation method, take a broken coal seam with complex structure and high risk of well wall instability as an experimental study object, test the sensitivity of the stability of the broken coal seam to the performance of drilling fluid, further optimize the drilling fluid system and the corresponding technical measures of collapse prevention of the coal seam, and improve the drilling engineering technology and development efficiency of deep coal seam gas. Disclosure of Invention The invention provides an experimental device and method for evaluating the stability of a broken coal seam by drilling fluid, and aims to solve the problems that in the prior art, the broken coal seam is broken in coal body structure, a core column cannot be drilled, and the stability of the broken coal seam cannot be evaluated effectively by the drilling fluid. Therefore, the invention provides an experimental device for evaluating the stability of drilling fluid on a broken coal seam,