CN110514524B - Experimental evaluation method for full-diameter shale reservoir core bedding fracture hydration strength - Google Patents
Experimental evaluation method for full-diameter shale reservoir core bedding fracture hydration strength Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/34—Purifying; Cleaning
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/003—Generation of the force
- G01N2203/0042—Pneumatic or hydraulic means
- G01N2203/0048—Hydraulic means
Abstract
The invention discloses a full-diameter shale reservoir core bedding crack hydration strength experimental evaluation method, which belongs to the field of unconventional oil and gas exploration and is characterized by comprising the following steps of: a. selecting a full-diameter core; b. drilling along the axial direction; c. putting the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole; d. pressurizing the stainless steel pump liquid pipe and the sealing rubber sleeve annulus; e. applying vertical pressure and confining pressure to the rock core at the same time; f. injecting liquid into a stainless steel pump liquid pipe, and starting a tracking pump to monitor the pump injection pressure; g. determining whether to end the experiment or change experiment parameters; h. taking out the core; i. changing vertical pressure or confining pressure; j. after lifting the stainless steel pump liquid tube for multiple times, tracking the pump injection pressure change and the pump injection liquid amount monitored by the pump in unit time; k. and evaluating the hydration strength of the rock core through the gas flow ratio. The method can deeply know the hydration characteristics of the shale gas reservoir, enrich the yield-increasing transformation theory of the shale reservoir and be beneficial to the yield increase of the shale reservoir.
Description
Technical Field
The invention relates to the field of unconventional oil and gas exploration, in particular to an experimental evaluation method for the bedding crack hydration strength of a full-diameter shale reservoir core.
Background
The hydraulic fracturing technology is a key technology for exploiting shale gas, and the complexity of a fracturing fracture network is one of important indexes of yield increase and transformation effects of shale reservoirs. The method has the advantages that the hydration characteristics of the shale gas reservoir are known, the essential differences of the shale gas reservoir and the conventional sandstone reservoir, including but not limited to basic physical properties of rock mechanics, mineral components under different geological conditions, a reservoir core pore-fracture structure, a bedding fracture development condition, reservoir core hydration characteristics and the like, are cleared, and the method is an important premise for improving shale gas development theory and technology.
At present, a small-diameter rock pillar with the diameter of 2.5cm is adopted for the shale reservoir water-rock effect, namely, the related indoor experiment of the hydration characteristic at home and abroad, and a multidirectional or unidirectional imbibition experiment is carried out, but because the small-diameter rock pillar has small contact area with liquid, the rock pillar has limited imbibition liquid amount and quickly reaches the boundary of the rock pillar, the long-time hydration experiment cannot be carried out, the hydration characteristic of the shale reservoir rock core is difficult to be fully known, and the influence of the change of the contact area of the rock pillar and the liquid and the overlying strata and the structural stress on the hydration strength and the law are not considered in the existing experiment method; bedding crack development is an important characteristic of a shale reservoir, but the influence of shale bedding on the core hydration strength is not researched, so that the related indoor experiment of the core hydration characteristic of the existing shale reservoir is difficult to deepen.
Chinese patent publication No. CN 104007049a, published as 2014, 08 and 27 discloses a method for classifying microscopic pores of shale, which is characterized by comprising the following steps: according to the basic form, the pore size is observed under a mirror and is divided into micropores and microcracks; classifying the micropores into organic matter pores, primary intergranular pores and secondary dissolution pores according to cause classification; carrying out refinement classification on micropores according to matrix components around the micropores and the position relation between the matrix components and the particles; according to the cause classification, the pore characteristics are observed under a mirror, and the microcracks are divided into bedding seams, structural seams, corrosion seams, diagenetic contraction seams and super-pressure seams.
The method for classifying the micro-pores of the shale disclosed by the patent document establishes a comprehensive classification scheme based on 'morphology-cause-component' by analyzing and researching the pore characteristics of the shale and follows a three-level classification principle, provides an effective characterization scheme for the research of the storage space of the shale reservoir, is convenient for further showing the relationship between different pore types and the storage performance, and is suitable for being applied to unconventional oil and gas exploration and development. However, the influence of the change of the contact area of the rock pillar and the liquid and the influence of the overlying strata and the structural stress on the hydration strength and the hydration law are not considered; the hydration characteristics of the shale gas reservoir cannot be deeply known, and the essential difference between the shale gas reservoir and the conventional sandstone reservoir is cleared, so that the yield-increasing transformation theory of the shale reservoir cannot be enriched, and the yield increase of the shale reservoir is not facilitated.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an experimental evaluation method for the bedding crack hydration strength of the full-diameter shale reservoir core.
The invention is realized by the following technical scheme:
a full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method is characterized by comprising the following steps:
a. selecting a full-diameter core with the length of more than 10cm and grinding the end face of the core;
b. drilling a full-diameter core axially by adopting an air cooling or liquid nitrogen cooling mode, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is more than 3 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean;
c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme;
d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular space pressure according to the material performance of the sealing rubber sleeve;
e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes;
f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed that the discharge capacity is less than 10ml/min, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in the stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of the experimental scheme, and starting a tracking pump to monitor the pumping pressure;
g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time;
h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment;
i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
k. and evaluating the hydration strength of the rock core through the ratio of the gas flow after the full-diameter rock core experiment to the gas flow before the experiment, wherein the larger the ratio is, the larger the bedding crack hydration strength of the rock core is.
In the step d, the annular pressure is 0.8-1 MPa.
In the step e, the step of applying the vertical pressure and the confining pressure to the rock core simultaneously means applying a vertical stress of 60MPa and a confining pressure of 10 MPa.
In the step g, the determination of whether to end the test according to the relation curve of the pump injection amount and the time refers to the end of the test when the increment of the total pump injection amount is less than 0.1ml after continuous 12 hours.
The beneficial effects of the invention are mainly shown in the following aspects:
1. the method comprises the following steps of (a) selecting a full-diameter core with the length of more than 10cm and grinding the end face of the core; b. Drilling a full-diameter core axially by adopting an air cooling or liquid nitrogen cooling mode, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is more than 3 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean; c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme; d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular space pressure according to the material performance of the sealing rubber sleeve; e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes; f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed that the discharge capacity is less than 10ml/min, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in the stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of the experimental scheme, and starting a tracking pump to monitor the pumping pressure; g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time; h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment; i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise; j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise; k. the hydration strength of the rock core is evaluated according to the gas flow ratio after the full-diameter rock core experiment and before the experiment, the higher the ratio is, the higher the hydration strength of the bedding seam of the rock core is, and the integral technical scheme is used.
2. According to the invention, the stress of overlying rocks is simulated by axial pressurization, the structural stress is simulated by applying circumferential stress, and the sealing is realized by adopting an internal and external double clamping manner, so that the method can be used for researching the hydration characteristics of the bedding joints of the shale reservoir and the influence manner and degree of the solid-liquid contact area on the hydration rule.
3. According to the invention, the full-diameter shale core is sealed by adopting an internal and external double clamping mode, overburden and structural stress synchronous pressurization is simulated, the influence experiment of different overburden structural stresses on the full-diameter core bedding seam hydration mode can be realized, and the full-diameter shale core bedding seam hydration strength evaluation can be realized.
4. According to the invention, the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve is placed into the hole, and the movable stainless steel pump liquid pipe internally provided with the sealing rubber sleeve is adopted, so that the change of the contact area between the inside of the rock core and the liquid can be effectively realized.
Drawings
The invention will be further described in detail with reference to the drawings and the detailed description, wherein:
FIG. 1 is a flow chart of an experiment for evaluating the bedding fracture hydration strength of a full-diameter shale reservoir core.
Detailed Description
Example 1
A full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method comprises the following steps:
a. selecting a full-diameter core with the length of 12cm and grinding the end face of the core;
b. adopting air cooling to axially drill a full-diameter core, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is 5 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean;
c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme;
d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular pressure according to the performance of the sealing rubber sleeve material, wherein the annular pressure is 0.8 MPa;
e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes;
f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed of 8ml/min of discharge capacity, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in a stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of an experimental scheme, and starting a tracking pump to monitor the pumping pressure;
g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time;
h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment;
i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
k. and evaluating the hydration strength of the rock core through the ratio of the gas flow after the full-diameter rock core experiment to the gas flow before the experiment, wherein the larger the ratio is, the larger the bedding crack hydration strength of the rock core is.
A, selecting a full-diameter core with the length of more than 10cm and grinding the end face of the core; b. drilling a full-diameter core axially by adopting an air cooling or liquid nitrogen cooling mode, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is more than 3 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean; c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme; d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular space pressure according to the material performance of the sealing rubber sleeve; e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes; f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed that the discharge capacity is less than 10ml/min, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in the stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of the experimental scheme, and starting a tracking pump to monitor the pumping pressure; g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time; h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment; i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise; j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise; k. the hydration strength of the rock core is evaluated according to the gas flow ratio after the full-diameter rock core experiment and before the experiment, the higher the ratio is, the higher the hydration strength of the bedding seam of the rock core is, and the integral technical scheme is used.
Example 2
A full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method comprises the following steps:
a. selecting a full-diameter core with the length of 13cm and grinding the end face of the core;
b. adopting air cooling to axially drill a full-diameter core, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is 8 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean;
c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme;
d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular pressure according to the performance of the sealing rubber sleeve material, wherein the annular pressure is 0.9 MPa;
e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes;
f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed of 6ml/min of discharge capacity, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in the stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of an experimental scheme, and starting a tracking pump to monitor the pumping pressure;
g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time;
h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment;
i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
k. and evaluating the hydration strength of the rock core through the ratio of the gas flow after the full-diameter rock core experiment to the gas flow before the experiment, wherein the larger the ratio is, the larger the bedding crack hydration strength of the rock core is.
The stress of overlying rocks is simulated by axial pressurization, the structural stress is simulated by applying circumferential stress, and the sealing is realized by adopting an internal and external double clamping mode, so that the method can be used for researching the hydration characteristics of the bedding joints of the shale reservoir and the influence mode and degree of the solid-liquid contact area on the hydration rule.
Example 3
A full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method comprises the following steps:
a. selecting a full-diameter core with the length of 15cm and grinding the end face of the core;
b. adopting air cooling to axially drill a full-diameter core, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is 10 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean;
c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme;
d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular pressure according to the performance of the sealing rubber sleeve material, wherein the annular pressure is 1 MPa;
e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes;
f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed of 5ml/min of discharge capacity, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in a stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of an experimental scheme, and starting a tracking pump to monitor the pumping pressure;
g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time;
h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment;
i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
k. the hydration strength of the rock core is evaluated according to the gas flow ratio of the whole-diameter rock core after the experiment and before the experiment, and if the ratio is larger, the rock-holding mode seals the whole-diameter shale rock core and simulates synchronous pressurization of overlying and structural stress, so that the higher the hydration strength of the bedding crack can be realized.
The experiment is influenced by the mode that the internal and external double-sandwich different overlying rock stratum structural stresses influence the hydration of the bedding seam of the full-diameter rock core, and the evaluation of the hydration strength of the bedding seam of the full-diameter shale rock core is realized.
Example 4
A full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method comprises the following steps:
a. selecting a full-diameter core with the length of 15cm and grinding the end face of the core;
b. adopting air cooling to axially drill a full-diameter core, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is 10 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean;
c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme;
d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular pressure according to the performance of the sealing rubber sleeve material, wherein the annular pressure is 1 MPa;
e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes;
f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed of 5ml/min of discharge capacity, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in a stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of an experimental scheme, and starting a tracking pump to monitor the pumping pressure;
g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time;
h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment;
i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
k. and evaluating the hydration strength of the rock core through the ratio of the gas flow after the full-diameter rock core experiment to the gas flow before the experiment, wherein the larger the ratio is, the larger the bedding crack hydration strength of the rock core is.
In the step e, the step of applying the vertical pressure and the confining pressure to the rock core simultaneously means applying a vertical stress of 60MPa and a confining pressure of 10 MPa.
In the step g, the determination of whether to end the test according to the relation curve of the pump injection amount and the time refers to the end of the test when the increment of the total pump injection amount is less than 0.1ml after continuous 12 hours.
By adopting the large-diameter core, the hydration rules and the strength of the core of the shale reservoir under different stress environments, liquid types and bedding joint development conditions are evaluated, the liquid system, the pumping mode and the flowback strategy of the shale reservoir under the bedding joint development conditions are optimized, the essential difference between the shale gas reservoir and a conventional sandstone reservoir is cleared for further understanding the hydration characteristics of the shale gas reservoir, so that the yield increasing and modifying theory of the shale reservoir is enriched, and the yield increasing of the shale reservoir is facilitated.
The stainless steel pump liquid pipe sleeved with the sealing rubber sleeve is placed into the hole, and the movable built-in stainless steel pump liquid pipe containing the sealing rubber sleeve is adopted, so that the change of the contact area between the inside of the rock core and liquid can be effectively realized.
Claims (4)
1. A full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method is characterized by comprising the following steps:
a. selecting a full-diameter core with the length of more than 10cm and grinding the end face of the core;
b. drilling a full-diameter core axially by adopting an air cooling or liquid nitrogen cooling mode, wherein the diameter of an eyelet is 2.5cm, and the distance from the drilling depth to the bottom of the core is more than 3 cm; cleaning debris in the holes and enabling the wall surfaces of the holes to be smooth and clean;
c. placing the stainless steel pump liquid pipe sleeved with the sealing rubber sleeve into the hole, confirming the distance between the stainless steel pump liquid pipe and the bottom of the hole according to the scale of the stainless steel pump liquid pipe, and calculating whether the solid-liquid contact area meets the requirements of the experimental scheme;
d. slowly pressurizing the stainless steel pump line and the annular space of the sealing rubber sleeve to enable the sealing rubber sleeve to be tightly attached to the wall surface of the hole, and determining the annular space pressure according to the material performance of the sealing rubber sleeve;
e. applying vertical pressure and confining pressure to the rock core simultaneously according to an experimental scheme, and stabilizing the pressure for 20 minutes;
f. slowly injecting liquid into the stainless steel pump liquid pipe at the speed that the discharge capacity is less than 10ml/min, calculating the liquid to be pumped according to the volume of a contact space formed by the stainless steel pump liquid pipe and the bottom of the hole and the volume in the stainless steel pump liquid pipe manifold, evaluating whether the liquid to be pumped meets the requirements of the experimental scheme, and starting a tracking pump to monitor the pumping pressure;
g. determining whether to end the experiment or change experiment parameters according to a relation curve of the pump injection amount and the time;
h. when the experiment is finished, firstly closing the tracking pump and stopping liquid injection, and then slowly unloading the vertical pressure and the confining pressure to the normal pressure; taking out the core, turning off the power supply and finishing the experiment;
i. the influence of an external pressure environment on the hydration strength of the bedding cracks of the shale reservoir is evaluated by changing the vertical pressure or the confining pressure and tracking the pump injection pressure change and the pump injection amount monitored by a pump in unit time; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
j. after the stainless steel pump liquid pipe is lifted for multiple times, the pump injection pressure change and the pump injection liquid amount monitored by the pump are tracked in unit time, and the influence of the solid-liquid contact area on the hydration strength of the bedding seams of the shale reservoir is evaluated; the higher the pumping pressure reduction times and the pressure drop value in unit time or the larger the pumping liquid injection amount in unit time, the larger the bedding crack hydration strength is, and the smaller the bedding crack hydration strength is otherwise;
k. and evaluating the hydration strength of the rock core through the ratio of the gas flow after the full-diameter rock core experiment to the gas flow before the experiment, wherein the larger the ratio is, the larger the bedding crack hydration strength of the rock core is.
2. The full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method as claimed in claim 1, is characterized in that: in the step d, the annular pressure is 0.8-1 MPa.
3. The full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method as claimed in claim 1, is characterized in that: in the step e, the step of applying the vertical pressure and the confining pressure to the rock core simultaneously means applying a vertical stress of 60MPa and a confining pressure of 10 MPa.
4. The full-diameter shale reservoir core bedding fracture hydration strength experimental evaluation method as claimed in claim 1, is characterized in that: in the step g, the determination of whether to end the test according to the relation curve of the pump injection amount and the time refers to the end of the test when the increment of the total pump injection amount is less than 0.1ml after continuous 12 hours.
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