Method for determining shale oil platform fracturing artificial fracture parameter observation coring well group

Abstract

The application discloses a kind of shale oil platform fracturing artificial fracture parameter observation coring well group determination method, steps include: step 1, selecting observation platform;Step 2, select observation horizontal well;Step 3, set fracturing parameter;Step 4, the fracture length and fracture height of observation horizontal well are observed, and monitoring is carried out;Step 5, design coring well group;Step 6, set up shale oil big platform well pattern.The method of the application has the characteristics of multiple well reference and reliable results, effectively solves the problem of unclear understanding of fracturing artificial fracture length and fracture height parameters, can quantitatively and intuitively statistics the hydraulic fracturing artificial fracture propagation parameters of Chinese continental facies multi-type shale oil reservoir under different fracturing modes, provides key support for shale oil big platform well pattern optimization and fracturing design, and effectively promotes the development process of continental facies shale oil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil field development, and relates to a shale oil platform fracturing artificial fracture parameter observation coring well group determination method. BACKGROUND

[0002] Downhole microseismic is the most mainstream technology for obtaining and testing fracturing fracture parameters at present. Microseismic monitoring is the signal of fracturing wave, and the actual fracture height and fracture length are far smaller than the distribution range of microseismic events. The well spacing of large platform horizontal wells refers to the microseismic fracture length, and the artificial fracture is insufficient to achieve full coverage of interwell reserves, so that the shale oil interwell reserve production is limited, and the transformation efficiency cannot be maximized. The interlayer thickness of three-dimensional development refers to the microseismic fracture height, and the artificial fracture is insufficient to achieve full production of vertical multi-layer sweet spots, so that the vertical reserve production is limited. Reducing the well spacing on the basis of microseismic may easily cause interwell channeling, resulting in increased water content and difficult single-well production. The specific parameters of artificial fractures under different transformation modes such as single-segment single-cluster, multi-segment few-cluster and large-segment multi-cluster are unknown, and the transformation mode suitable for different shale oil reservoirs and the transformation effect are difficult to evaluate. Domestic related oil fields have tried to take core observation of hydraulic fractures downhole, but no fracturing cracks have been observed due to improper design. Although the core observation of fracturing cracks has been realized in North America, no quantitative statistical core well group design method for fracture length, fracture height and fracture width has been formed.

[0003] Shale oil has become a huge pillar to ensure the stable production of more than 200 million tons of crude oil in China, and it is of great significance to promote the efficient development of continental shale oil to determine the key parameters of hydraulic fracture network. Therefore, it is urgent to develop a shale oil platform fracturing artificial fracture parameter observation coring well group method to provide an effective reference for the deployment of horizontal wells using the same development means for low-permeability oil and gas reservoirs and shale gas. SUMMARY

[0004] The purpose of the present application is to provide a shale oil platform fracturing artificial fracture parameter observation coring well group determination method, which solves the problem that it is difficult to realize quantitative statistics of fracture length, fracture height and fracture width in the core observation of fracturing cracks in the prior art.

[0005] The technical scheme adopted by the present application is a shale oil platform fracturing artificial fracture parameter observation coring well group determination method, which is implemented according to the following steps:

[0006] Step 1, selecting an observation platform;

[0007] Step 2, selecting an observation horizontal well;

[0008] Step 3, setting fracturing parameters;

[0009] Step 4, observing the fracture length and fracture height of the horizontal well and monitoring;

[0010] Step 5, design coring well group;

[0011] Step 6, set up shale oil large platform well pattern.

[0012] The beneficial effect of the present application is that, by designing the coring well group of the hydraulic fracturing horizontal well, by designing the key steps such as the selection of the typical platform, the selection of the observation horizontal well, the design of the fracturing parameter, the design of the fracture test, and the design of the coring well group, the coring well group design method for quantitatively counting the fracture network parameters of the hydraulic fracturing artificial fracture is determined, which has the characteristics of multi-well reference and reliable result, and effectively solves the problem of unclear understanding of the parameters such as the fracture length and the fracture height of the fracturing artificial fracture. The technical means can quantitatively and intuitively count the hydraulic fracturing artificial fracture expansion parameters of the Chinese continental shale oil reservoir under different fracturing modes, provides key support for the shale oil large platform well pattern optimization and fracturing design, and effectively promotes the continental shale oil revolution process. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1a is a schematic diagram of the fracture height observation horizontal well group design of the embodiment 1 of the present application;

[0014] Figure 1b is a schematic diagram of the fracture height observation horizontal well group design of the embodiment 1 of the present application;

[0015] Figure 2a is a schematic diagram of the fracture length observation horizontal well group design of the embodiment 1 of the present application;

[0016] Figure 2b is a schematic diagram of the fracture length observation horizontal well group design of the embodiment 1 of the present application;

[0017] Figure 3 is a platform fracture analysis diagram of QH41 of the embodiment 2 of the present application;

[0018] Figure 4 is a geological quality analysis diagram of QH41-4 well of the embodiment 2 of the present application;

[0019] Figure 5a is a sand body thickness plan of Chang 71 of the QH41 platform of the embodiment 2 of the present application;

[0020] Figure 5b is an oil saturation plan of Chang 71 of the QH41 platform of the embodiment 2 of the present application;

[0021] Figure 5c is a porosity plan of Chang 71 of the QH41 platform of the embodiment 2 of the present application;

[0022] Figure 5d is a brittleness coefficient plan of Chang 71 of the QH41 platform of the embodiment 2 of the present application;

[0023] Figure 6 is a three-dimensional schematic diagram of the QH41 observation well of the embodiment 2 of the present application;

[0024] Figure 7a is a longitudinal fracture height observation well fracturing design diagram of the embodiment 2 of the present application;

[0025] Figure 7b is a planar fracture length observation well fracturing design diagram of the embodiment 2 of the present application;

[0026] Figure 8a is a fold microseismic monitoring fracture height statistical diagram of the JH41-3 well of the embodiment 2 of the present application;

[0027] Figure 8b is a microseismic fracture length parameter statistical diagram of the JH41-3 well of the embodiment 2 of the present application. DETAILED DESCRIPTION

[0028] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0029] The method of the present application realizes quantitative statistics of key parameters of fracturing artificial fracture length and fracture height through accurate design of a coring well group, and is implemented according to the following steps:

[0030] Step 1, selecting an observation platform,

[0031] In order to ensure the representativeness of coring observation, the selection of the observation platform needs to meet the following five principles: ① The oil layer within 300m of the horizontal well root is weak in heterogeneity, and the planar and longitudinal distribution is stable; ② The fracture in the observation platform range is basically not developed, and there is no large fault or fracture communication in the longitudinal and planar directions; ③ The observation platform horizontal well direction is perpendicular to the maximum principal stress, and the number of wells is greater than four; ④ The observation platform does not belong to the development superposition area; ⑤ No blowout and overflow events occur during the drilling process of the observation platform, and the cementing quality of the horizontal well root is qualified.

[0032] Step 2, selecting an observation horizontal well,

[0033] At least two and more horizontal wells are selected as key observation horizontal wells within the observation platform, at least one of which is mainly used to monitor the longitudinal fracture height, and at least another one of which is mainly used to monitor the planar fracture length, the two wells are verified with each other to ensure the accuracy of the fracture parameter acquisition; through three-dimensional geological modeling and mechanical modeling, it is ensured that the selected observation horizontal well is stable in reservoir thickness, similar in brittleness coefficient and small in stress difference between the two sides within 500m range of the root (or left and right directions).

[0034] Step 3, setting fracturing parameters,

[0035] The longitudinal fracture height observation horizontal well root adopts three kinds of fracturing modes of single section single cluster, multi-section few clusters and large section multiple clusters, each kind of fracturing mode has at least two, and is separated respectively, different fracturing modes are supported by different color proppants, which is convenient to distinguish different fracturing mode fracture height;

[0036] At the same time, the plane fracture length observation horizontal well root adopts one of the three modes of single section single cluster, multi-section few clusters and large section multiple clusters (other modes can be added observation horizontal well alone), and the number of designed sections is at least more than eight, which ensures the accuracy of the fracture length parameter; since the two observation horizontal wells are adjacent, the proppant of the fracture of the well is not dyed.

[0037] Step 4, observe the fracture length and fracture height of the observation horizontal well, and monitor,

[0038] The downhole microseismic or sonar far-probing fracture monitoring technology is used for the key observation horizontal well to obtain the key fracture test parameters of the fracture length and fracture height of the key observation horizontal well; at the same time, the downhole television hole abrasion monitoring is carried out on the observation horizontal well to ensure that the opening rate of each cluster of the fracturing design section of the observation horizontal well root is more than 80%, and the effect of hydraulic fracturing reconstruction is obvious.

[0039] Step 5, design the coring well group, the specific process is:

[0040] 5.1) Set up a longitudinal fracture height observation horizontal well group,

[0041] The longitudinal fracture height monitoring coring well group is designed for four wells, including two high-angle coring wells and two horizontal wells, and the embodiment 1 is shown in Figure 1a 、 Figure 1b ,

[0042] First, two high-angle coring wells are implemented, the plane projection of the high-angle coring well is parallel to the observation horizontal well, the plane distance between the high-angle coring well and the observation horizontal well is less than 10% of the fracture test half fracture length, and the two high-angle coring wells are symmetrical around the observation horizontal well (X1, X2), wherein the X1 well is cored from the top of the reservoir to the bottom, and the X2 well is cored from the bottom of the reservoir to the top of the formation, the vertical distance of the two wells through the reservoir must be greater than the average value of the fracture test upper fracture height of the reservoir; the vertical distance of the two wells through the reservoir must be greater than the average value of the fracture test lower fracture height of the reservoir, and the coring section microseismic event point is active;

[0043] Then, based on the observation of artificial fractures in two high-deviation coring wells, two horizontal coring wells (P1, P2) are symmetrically arranged on both sides of the observation horizontal well, the distance between the horizontal coring well and the observation horizontal well is 1 / 2 of the distance between the high-deviation coring well and the observation horizontal well, wherein P1 well is located above the reservoir, and the coring direction is the line connecting the highest points O1→O2 of the artificial fractures in the two high-deviation coring wells; P2 well is located below the reservoir, and the coring direction is the line connecting the highest points O3→O4 of the artificial fractures in the two high-deviation coring wells. See Figure 1a , Figure 1b ;

[0044] The vertical distance between the observable artificial fractures in the P1 and P2 wells and the middle of the oil layer is calculated, and the average values are taken as the actual upper and lower fracture heights of the fracturing.

[0045] 5.2) Set up a horizontal well group for observing the length of planar fractures,

[0046] The horizontal well group for observing the length of planar fractures is composed of four horizontal coring wells. See Figure 2a , Figure 2b ;

[0047] First, two horizontal coring wells B1 and B2 are implemented, the distance between the two horizontal coring wells B1 and B2 and the minimum distance of the fracture length observation horizontal well is less than 10% of the fracture test half fracture length, and the maximum distance is the average value of the half fracture length, one coring well is taken from the observation horizontal well to the far end, and the other coring well is taken from the observation horizontal well to the near end;

[0048] Then, the maximum points O5 and O6 of the artificial fracture coring observation half fracture length of the two horizontal coring wells B1 and B2 are obtained, and two coring wells B3 and B4 are set up in the direction of the line connecting O5 and O6 and symmetrically around the observation horizontal well.

[0049] Then, the vertical distance between all the artificial fractures observed by the two coring wells B3 and B4 and the observation horizontal well is calculated, and the average values are taken as the left and right half fracture lengths of the artificial fractures.

[0050] Step 6, set up a large platform well pattern for shale oil,

[0051] According to the half fracture length and fracture height data obtained in step 5, the horizontal well spacing of the single-layer development platform for shale oil is greater than or equal to the fracture length calculated by the coring well group (not more than 10% of the statistical value), and the vertical development platform vertical interlayer thickness is greater than or equal to the fracture height calculated by the coring well group (not more than 10% of the statistical value), and accordingly the large platform well pattern for shale oil is set up.

[0052] Example 1

[0053] The procedure of Example 1 is referred to the aforementioned method procedure, the parameters involved and the corresponding results have been described with the procedure. The results show that the method of the present application can be reliably implemented, and the results are accurate.

[0054] Example 2

[0055] China Petroleum Changqing Oilfield launched the first shale oil hydraulic fracturing test field construction in China, through the core hole to re-understand the artificial fracture, to optimize well pattern spacing, segment cluster design, fracturing sequence and study to provide reference for improving recovery, to promote the upgrading of unconventional oil and gas development technology, the specific process is as follows:

[0056] 1) Select observation platform,

[0057] Use the three-dimensional seismic interpretation to analyze the fault development of Qing H41 platform (see Figure 3 ), the horizontal well deployment direction is perpendicular to the maximum principal stress, the platform deployment well number is 5, which meets the requirements, and it does not belong to the development superposition area. The geological quality analysis shows that the horizontal well root is a three-dimensional sweet spot distribution area (see Figure 4 ), which meets the basic selection principle of observation platform.

[0058] 2) Select observation horizontal well,

[0059] Through three-dimensional geological modeling, Qing H41 selects the observation horizontal well root within the range of 500m on both sides, the reservoir thickness is stable, the brittleness coefficient is similar, and the stress difference on both sides is small (see Figure 5a 、 Figure 5b 、 Figure 5c 、 Figure 5d ). Select two adjacent wells as observation wells, and distribute as fracture height and fracture length observation horizontal wells. Since the core drilling focuses on observing the fracturing effect, this test field does not obtain well pattern quantitative parameters according to the design of well group, but the selection ideas of observation platform and observation horizontal well are consistent.

[0060] 3) Set fracturing parameters,

[0061] Qing H41-3 well is a longitudinal fracture height observation horizontal well, the root adopts single segment single cluster, multi-segment few clusters and large segment multi-cluster three fracturing modes, each fracturing mode has at least two, and is separated respectively. Different fracturing modes use different color proppant support to distinguish different fracturing mode fracture height;

[0062] Qing H41-4 well is a plane fracture length observation horizontal well, the root adopts multi-segment few cluster mode to be designed separately. In order to distinguish the fracture, the proppant of this well is not dyed (see Figure 7a 、 Figure 7b ).

[0063] 4) Perform fracture test,

[0064] The fracture length and fracture height data obtained by microseism are used as the design basis of the coring well. Figure 8a , Figure 8b ).

[0065] 5) setting the coring well group,

[0066] Since the focus of this coring is to observe the fracturing effect, the test field does not obtain the quantitative parameters of the well pattern according to the design of the well group, but refers to the design idea of the coring well group. According to the design of the high-angle coring well parallel to Q41-3, the average half fracture length of the earthquake is 300m, the high-angle distance is 30m from the horizontal well, and the minimum distance of the horizontal coring well from Q41-4 well is 30m, which is set from near to far (see Figure 6 ). At present, the high-angle coring well has observed the fracturing sand and monitored the actual fracture height under the single-stage single-cluster fracturing according to the design. It shows that the method of the application conforms to the design idea of quantitative acquisition of fracture parameters, and the well pattern parameters obtained by the method of the application effectively improve the reserve producing degree and single well production, and provide support for shale oil production increase.

[0067] Example 3

[0068] In the early stage, the coring observation of the fracturing crack was carried out in the YP well field, and on the basis of the microseismic analysis, the coring was started at a position 170m away from YP3 well and 140m away from YP4 well, and the longitudinal continuous coring in the long 7 section was carried out for a total of 141.95m, and no fracturing crack was found. The main reason is that the distance between the coring well and the fracturing well should not be too long. Therefore, the fracture length monitoring well must start coring from the target well, and ensure that the fracturing crack can be observed. The Q41-4 well is designed by this method, and the fracturing crack is observed, and the purpose of quantitative statistics of half fracture length is achieved. It shows that the method of the application conforms to the design idea of quantitative acquisition of fracture parameters.

[0069] Example 4

[0070] In the early stage, the coring was carried out in the An 239-24 well (directional well) plane distance 80m in the upper part of the oil layer, and the coring was carried out in the microseismic coverage range of 85m, and no support crack was found. It shows that the place where the microseismic event is dense does not necessarily exist the fracturing crack, and the fracture height monitoring well must be closer to the observation well. The Q41-3 well is designed by this method, and the coring is carried out at a distance of 30m from the horizontal well, and the fracturing crack is observed. It shows that the method of the application conforms to the design idea of quantitative acquisition of fracture parameters.

Claims

1. A method for determining a group of shale oil platform fracturing artificial fracture parameter observation coring wells, characterized in that, The following steps are implemented: Step 1, select an observation platform; Step 2, select an observation horizontal well; Step 3, set the fracturing parameters; Step 4, observe the fracture length and height of the horizontal well and monitor it; Step 5, design a coring well group, the specific process is: 5.1) Set up a longitudinal fracture height observation horizontal well group: a total of four longitudinal fracture height monitoring coring wells are designed, including two high-angle coring wells and two horizontal coring wells; First, implement two high-angle coring wells X1 and X2, the high-angle coring well plane projection is parallel to the longitudinal fracture height observation horizontal well, the distance between the high-angle coring well plane and the longitudinal fracture height observation horizontal well is less than 10% of the fracture test half fracture length, and the two high-angle coring wells are symmetrically arranged on both sides of the longitudinal fracture height observation horizontal well, wherein the X1 well is cored from the top of the reservoir to the bottom of the reservoir, and the X2 well is cored from the bottom of the reservoir to the top of the reservoir, the vertical distance of the two wells through the reservoir must be greater than the average value of the fracture test upper fracture height of the reservoir; the vertical distance of the two wells through the reservoir must be greater than the average value of the fracture test lower fracture height of the reservoir, and the microseismic event point is active in the coring section; Then, based on the artificial fracture observation of the two high-angle coring wells, two horizontal coring wells P1 and P2 are symmetrically arranged on both sides of the longitudinal fracture height observation horizontal well, the distance between the horizontal coring well and the longitudinal fracture height observation horizontal well is 1 / 2 of the distance between the high-angle coring well and the longitudinal fracture height observation horizontal well, wherein the P1 well is located above the reservoir, and the coring direction is the line connecting the highest points O1→O2 of the artificial fracture coring observation of the two high-angle coring wells; the P2 well is located below the reservoir, and the coring direction is the line connecting the highest points O3→O4 of the artificial fracture coring observation of the two high-angle coring wells; the vertical distance of the artificial fracture observed by the P1 and P2 wells from the middle of the oil layer is calculated, and the average value is taken as the actual upper and lower fracture heights of the fracturing; 5.2) Set up a plane fracture length observation horizontal well group: a total of four horizontal coring wells are arranged in the plane fracture length observation horizontal well group; First, implement two horizontal coring wells B1 and B2, the minimum distance between the two horizontal coring wells B1 and B2 and the plane fracture length observation horizontal well is less than 10% of the fracture test half fracture length, and the maximum distance is the average value of the half fracture length, one horizontal coring well is cored from the plane fracture length observation horizontal well to the far end, and the other horizontal coring well is cored from the plane fracture length observation horizontal well to the near end; Then, the artificial fracture coring observation half fracture length maximum points O5 and O6 of the two horizontal coring wells B1 and B2 are obtained, and two horizontal coring wells B3 and B4 are arranged in the direction of the line connecting O5 and O6 and the direction symmetrically around the plane fracture length observation horizontal well; the vertical distance of all artificial fractures observed by the two horizontal coring wells B3 and B4 from the plane fracture length observation horizontal well is calculated, and the average value is taken as the left and right half fracture lengths of the artificial fracture; Step 6, set up a shale oil large platform well pattern.

2. The shale oil platform fracturing artificial fracture parameter observation coring well group determination method according to claim 1, characterized in that, In step 1, the selection of the observation platform needs to meet the following five principles: ① The heterogeneity of the oil layer within 300 m of the horizontal well root is weak, and the planar and longitudinal distribution is stable; ② The faults in the observation platform range are basically not developed, and there are no large faults or cracks in the longitudinal and planar directions; ③ The horizontal well direction of the observation platform is perpendicular to the maximum principal stress, and the number of wells is greater than four; ④ The observation platform does not belong to the development superposition area; ⑤ There are no blowout and overflow events during the drilling process of the observation platform, and the cementing quality of the horizontal well root is qualified. In step 2, the specific process is:

3. The method of claim 1, wherein: Two adjacent horizontal wells are selected as key observation horizontal wells within the observation platform, one of which is used to monitor the longitudinal fracture height, and the other is used to monitor the planar fracture length; through three-dimensional geological modeling and mechanical modeling, the key observation horizontal wells are selected to ensure that the reservoir thickness within 500 m on both sides of the root is stable, the brittleness coefficient is similar, and the stress difference on both sides is small. In step 3, the specific process is:

4. The method of claim 3, wherein: The root of the longitudinal fracture height observation horizontal well adopts three fracturing modes of single segment single cluster, multi-segment few clusters and large segment multiple clusters, and each mode has at least two, and is separated, and different fracturing modes use different colored proppant support; At the same time, the root of the planar fracture length observation horizontal well adopts one of the three modes of single segment single cluster, multi-segment few clusters and large segment multiple clusters, and the number of segments is at least more than eight to ensure the accuracy of the fracture length parameters; Since the two key observation horizontal wells are adjacent, in order to distinguish the fractures, the proppant of the planar fracture length observation horizontal well is not dyed. In step 4, the specific process is:

5. The method of claim 1, wherein: The key observation horizontal wells are monitored by downhole microseismic or sonar far-probe fracture monitoring technology to obtain key fracture test parameters such as fracture length and fracture height of the key observation horizontal wells; at the same time, the downhole television hole erosion condition monitoring of the key observation horizontal wells is carried out to ensure that the opening rate of each cluster of the key observation horizontal well root fracturing design segment is greater than 80%, and the hydraulic fracturing reconstruction effect is ensured. In step 6, the specific process is:

6. The method of claim 1, wherein: According to the half fracture length and fracture height data obtained in step 5, the horizontal well spacing of the single-layer development shale oil platform is greater than or equal to the fracture length of the coring well group statistics, and the vertical development platform longitudinal interlayer thickness is greater than or equal to the fracture height of the coring well group statistics, and the shale oil large platform well pattern is set accordingly. ​

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