Comprehensive channeling prevention method for reducing inter-well pressure channeling proportion

Abstract

The invention discloses a comprehensive anti-channeling method for reducing the inter-well pressure channeling proportion, which is characterized in that a fracture zone, a water-containing natural large crack and a waterline are avoided through source avoidance, and the pressure channeling probability in the fracturing process is reduced; the expansion of the hydraulic fractures of two adjacent wells is not overlapped, so that pressure channeling caused by expansion intersection of the two hydraulic fractures is avoided; through temporary plugging prevention, a hydraulic fracture is prevented from communicating with an old fracture and a natural fracture zone, an in-fracture temporary plugging agent is added to a fracturing section where pressure channeling possibly occurs, the in-fracture temporary plugging agent forms a filter cake after reaching a fracture tip, expansion of the fracture tip is further inhibited, the net pressure in the fracture is improved, and therefore the fracture turns. In the fracture zone, the temporary plugging agent in the crack can be gathered to form a plugging layer, so that the crack is turned, and pressure channeling is avoided.

Description

Technical Field

[0001] The present invention relates to the field of oil and natural gas fracturing, and in particular to a comprehensive anti-channeling method for reducing the pressure channeling ratio between wells. Background Art

[0002] At present, hydraulic fracturing technology has become the main development technology for unconventional reservoirs. However, due to the large-scale fracturing transformation and randomness of fracture expansion in unconventional reservoirs, the possibility of hydraulic channeling in unconventional reservoirs is greatly increased. Hydraulic channeling often leads to increased water content in adjacent producing wells, decreased daily oil production, and serious interference with the production of adjacent wells. Therefore, reducing hydraulic channeling between wells is of great practical significance.

[0003] Conventional anti-channeling fracturing methods typically optimize parameters through numerical simulation. Parameter optimization methods for conventional tight reservoir fracturing include evaluating and classifying the reservoir's energy enhancement potential to obtain evaluation results; deploying channeling test wells based on the evaluation results, resulting in test and evaluation wells; conducting inter-channeling tests on the test and evaluation wells, and correcting the fracture propagation calculation model and critical construction conditions after field construction; and calculating inter-well fracture propagation based on the corrected fracture propagation calculation model, setting different geological and well construction conditions, and obtaining anti-channeling construction parameters using the corrected critical construction conditions as the upper limit. However, due to the high heterogeneity of unconventional reservoirs, factors such as faults, natural fractures, waterlines, and old well deficits significantly influence hydraulic fracture propagation, making conventional anti-channeling parameter optimization difficult to effectively apply to unconventional reservoirs. Summary of the Invention

[0004] The purpose of the present invention is to provide a comprehensive anti-channeling method for reducing the pressure channeling ratio between wells. The method is an anti-channeling measure with strong applicability and operability.

[0005] The purpose of the present invention is to achieve a comprehensive anti-channeling method for reducing the pressure channeling ratio between wells through the following technical means, including:

[0006] Source avoidance: Through 3D seismic and well logging interpretation, the locations of faults and natural fractures are obtained, and the locations of fracturing seams are arranged to avoid faults and natural fractures.

[0007] Staggered seam layout: three-dimensional staggered seam layout is used to stagger the fractures of adjacent wells or parent wells and child wells. The fractures are staggered on the plane to avoid direct fracture channeling. For multi-layer shale oil and gas reservoirs, three-dimensional staggered well layout is used to reduce vertical pressure channeling interference and ensure that the hydraulic fractures of adjacent wells do not overlap.

[0008] Temporary plugging prevention: In the fracturing sections of old wells, overlapping areas and adjacent fracture locations, granular temporary plugging agents are pumped in the early stages of the pre-fluid or sand-carrying fluid to seal the natural or artificial fractures in the fault zone, and the scale of fracturing transformation is reduced during fracturing.

[0009] Specifically, the fault avoidance is to obtain the location of the fault zone based on 3D seismic and well logging interpretation, and not to perform perforation fracturing within 30 meters of the fault in the fracturing section where the fault and the well intersect.

[0010] The specific way to avoid natural fractures is to determine the location of large natural fractures through well logging interpretation, specifically logging blueprint resistance. In the fracturing section where the large fracture and the well intersect, no perforation fracturing is carried out within 20 meters of the large fracture.

[0011] In actual construction, if two hydraulic fractures may intersect while expanding along the maximum horizontal principal stress, the perforation and fracturing positions of the fracturing well should be adjusted to avoid the intersection of the two hydraulic fractures and the resulting pressure channeling.

[0012] In areas with water injection wells, horizontal wells shall not be perforated or fractured within 20 meters from the waterline.

[0013] In the temporary blocking prevention, the granular temporary blocking agent is DA-2 blocking agent.

[0014] During the fracturing process, the wellhead pressure of the adjacent well rises rapidly, so the fracturing construction is stopped and a small-particle temporary plugging agent is pumped with clean water to seal the cracks.

[0015] The beneficial effects of the present invention are: by avoiding the source, thus avoiding fault zones, large water-bearing natural fractures, and waterlines, the probability of hydraulic channeling during fracturing is reduced; by preventing the hydraulic fractures of two adjacent wells from overlapping, the intersection of the two hydraulic fractures and causing hydraulic channeling is avoided; by preventing hydraulic fractures from connecting with old fractures and natural fault zones through temporary plugging, a temporary plugging agent is added to the fracturing section where hydraulic channeling may occur. The temporary plugging agent forms a filter cake after reaching the fracture tip, further inhibiting the expansion of the fracture tip, increasing the net pressure within the fracture, and thus causing the fracture to redirect. Within the fault zone, the temporary plugging agent can aggregate to form a plugging layer, causing the fracture to redirect and preventing hydraulic channeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the distribution map of platform fault plane;

[0017] Figure 2 It is a suspected fracture map of the well logging blueprint;

[0018] Figure 3 This is the fracturing waterline avoidance diagram;

[0019] Figure 4 This is a simulation diagram of a hydraulic fracture;

[0020] Figure 5 This is a schematic diagram of temporary blocking and anti-channeling;

[0021] Figure 6 This is the distribution map of the fracture plane of platform A;

[0022] Figure 7 This is a schematic diagram of the three-dimensional staggered seams of platform A;

[0023] Figure 8 This is the fracturing curve of the channeling control section of platform A;

[0024] Figure 9 Schematic diagram of a comprehensive anti-channeling method to reduce the pressure channeling ratio between wells;

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0026] [Example 1]

[0027] A comprehensive anti-channeling method for reducing the pressure channeling ratio between wells, comprising:

[0028] like Figure 1 and Figure 9 As shown, source avoidance is achieved through 3D seismic and well logging interpretation to obtain the locations of faults and natural fractures, and the locations of fracturing are used to avoid faults and natural fractures.

[0029] Specifically, the fault avoidance is to obtain the location of the fault zone based on 3D seismic and well logging interpretation, and not to perform perforation fracturing within 30 meters of the fault in the fracturing section where the fault and the well intersect.

[0030] The specific way to avoid natural fractures is to determine the location of large natural fractures through well logging interpretation, specifically logging blueprint resistance. In the fracturing section where the large fracture and the well intersect, no perforation fracturing is carried out within 20 meters of the large fracture.

[0031] In areas with water injection wells, horizontal wells shall not be perforated or fractured within 20 meters from the waterline.

[0032] Preliminary data statistics and analysis show that pressure channeling is mainly affected by fault zones, natural cracks and the scale of transformation. Pressure channeling is a comprehensive problem, so it is necessary to prevent channeling from multiple aspects.

[0033] The first step is to avoid the source. 3D seismic data combined with detailed well logging interpretation can identify the locations of faults and natural fractures, and then avoid them when placing fracturing sites. Areas prone to pressure channeling should be avoided before fracturing.

[0034] Source avoidance includes fractures, large cracks and water lines, e.g. Figure 1 The figure shows the plane seismic interpretation of a certain platform. There are two large fault zones near West 117 in the lower left part of the figure. The fracturing section where the fault intersects with West 79 well should strengthen the corresponding anti-channeling measures, and no perforation or fracturing should be carried out within 30 meters of the fault.

[0035] The resistance of the logging blueprint shows a sudden and obvious decrease, indicating that the reservoir location may be a large fracture with a high water content in the formation, resulting in a sudden decrease in resistance, as shown below Figure 2 As shown, in the fracturing section where the large fracture intersects the well, perforation and fracturing are not performed within 20 meters of the large fracture. Perforation and fracturing are not performed within a minimum range of 10 meters from the large fracture, and within a maximum range of 15 meters.

[0036] For areas with water injection wells, the water injection line may also cause pressure channeling, resulting in a large amount of water output from the oil wells, as shown below Figure 3 As shown, the horizontal well passes through two water lines. To avoid pressure channeling, no perforation or fracturing is performed within 20 meters from the water line, which is the rectangular area in the figure.

[0037] Staggered seam layout: three-dimensional staggered seam layout is used to stagger the fractures of adjacent wells or parent wells and child wells. The fractures are staggered on the plane to avoid direct fracture channeling. For multi-layer shale oil and gas reservoirs, three-dimensional staggered well layout is used to reduce vertical pressure channeling interference and ensure that the hydraulic fractures of adjacent wells do not overlap.

[0038] In actual construction, if two hydraulic fractures may intersect while expanding along the maximum horizontal principal stress, the perforation and fracturing positions of the fracturing well should be adjusted to avoid the intersection of the two hydraulic fractures and the resulting pressure channeling.

[0039] The second step is staggered fracture placement: For fracturing wells with a small distance between adjacent wells and the potential for fracture crossover, a three-dimensional staggered fracture placement design is implemented to ensure that the fractures of the adjacent wells or parent wells and the child wells are staggered. The fracture placement locations are determined.

[0040] like Figure 4 As shown in the figure, based on field practice and numerical simulation calculations, the length and height of the hydraulic fracture extension are calculated, the liquid and sand amounts of the fracturing are optimized, and the extension length of the hydraulic fracture is controlled so that the hydraulic fractures of two adjacent wells do not overlap. At the same time, if the two fractures may intersect during the process of extending along the maximum horizontal principal stress, the perforation and fracturing position of the fracturing well should be adjusted to avoid the intersection of the two hydraulic fractures and cause pressure channeling.

[0041] Temporary plugging prevention: In the fracturing sections of old wells, overlapping areas and adjacent fracture locations, granular temporary plugging agents are pumped in the early stages of the pre-fluid or sand-carrying fluid to seal the natural or artificial fractures in the fault zone, and the scale of fracturing transformation is reduced during fracturing.

[0042] In the temporary blocking prevention, the granular temporary blocking agent is DA-2 blocking agent.

[0043] The third step is to reduce the scale of fracturing in older wells, overlapping areas, and fracturing sections near fractures while using a small-particle temporary plugging agent to prevent channeling. This small-particle temporary plugging agent is pumped into the pre-fracturing fluid or sand-carrying fluid during the initial stages of the fracturing process to seal natural or artificial fractures in the fault zone.

[0044] like Figure 5 As shown, to prevent hydraulic fractures from bridging existing fractures and natural fault zones, a temporary plugging agent is added to the fracture section where pressure channeling is likely to occur. The temporary plugging agent (white spots) forms a filter cake after reaching the fracture tip, further inhibiting the expansion of the fracture tip and increasing the net pressure within the fracture, thereby redirecting the fracture. Within the fault zone, the temporary plugging agent aggregates to form a sealing layer, redirecting the fracture and preventing pressure channeling.

[0045] During the fracturing process, the wellhead pressure of the adjacent well rises rapidly, so the fracturing construction is stopped and a small-particle temporary plugging agent is pumped with clean water to seal the cracks.

[0046] The fourth step is to make real-time adjustments to deal with situations that arise during the fracturing process. Since the fault zone spans a large area and the location of natural fractures is difficult to predict, when fracturing occurs, small-particle temporary plugging agents can be added and the displacement can be reduced to make real-time adjustments to reduce the negative impact of fracturing.

[0047] Specifically, taking platform A as an example,

[0048] Platform A has a total of 5 horizontal wells, with an average horizontal section length of 3,154 meters and an oil layer drilling rate of 72.6%.

[0049] Step 1: Combine 3D seismic and logging interpretation to avoid the source of faults and natural fractures during segment and cluster selection. For horizontal segments with obvious fractures shown in logging interpretation, avoidance distance of no less than 30 meters for segment and cluster selection of large faults, and 15 meters for conventional avoidance. Figure 6 The black box part on the line from Hua H90-2 to Hua H90-6 is the fracture interpreted by well logging.

[0050] Step 2: Use software to draw the wellbore trajectory and fracture distribution map according to the actual fracturing sequence, such as Figure 7 As shown, the intersection distance between the hydraulic fractures of adjacent wells or old wells and new wells is greater than 10 meters.

[0051] Step 3: For adjacent fractures and fracturing sections that may experience channeling, small-particle temporary plugging agents are used to prevent channeling. This test case uses the DA-2 plugging agent commonly used in Changqing Oilfield as an example. DA-2 plugging agent is pumped into the pre-fluid or sand-carrying fluid at the early stage. The dosage for a single section is 100 to 200 kg. The dosage can be adjusted according to the size of the fracture to plug natural or artificial fractures in the fracture zone.

[0052] Table 1 Performance indexes of DA-2 temporary plugging diverter

[0053]

[0054] Table 2DA-2 Temporary plugging pump injection procedure

[0055]

[0056]

[0057] Step 4: If the wellhead pressure of the adjacent well is found to rise rapidly during the fracturing process, it indicates that channeling has occurred. The fracturing construction should be stopped immediately and 100 to 200 kg of plugging agent should be pumped with clean water. The amount can be adjusted according to the size of the channeling crack. Fracturing construction can be resumed after the temporary plugging agent has blocked the crack.

[0058] like Figure 8 As shown in the figure, during the fracturing process on site, when Well A was fracturing the 33rd section, due to the relatively developed fault zone adjacent to the fracturing section, pressure channeling still occurred on the basis of a certain avoidance. The wellhead pressure of the adjacent well rose from 3.1MPa to 4.6MPa, showing obvious pressure channeling characteristics. After this characteristic appeared, the fracturing construction was immediately stopped, and then 200kg of DA-2 plugging agent was pumped into Well A. Subsequently, the wellhead pressure of the adjacent wells was closely monitored. There was no pressure increase in the adjacent wells, indicating that the pressure channeling control achieved good results and the fracturing construction of this section was carried out normally.

Claims

1. A comprehensive anti-channeling method for reducing the pressure channeling ratio between wells, characterized by: Including source avoidance, obtaining the location of faults and natural fractures through 3D seismic and well logging interpretation, and avoiding faults and natural fractures by fracturing locations. Staggered seam layout: three-dimensional staggered seam layout is used to stagger the fractures of adjacent wells or parent wells and child wells. The fractures are staggered on the plane to avoid direct fracture channeling. For multi-layer shale oil and gas reservoirs, three-dimensional staggered well layout is used to reduce vertical pressure channeling interference and ensure that the hydraulic fractures of adjacent wells do not overlap. Temporary plugging prevention: In the fracturing sections of old wells, overlapping areas and adjacent fracture locations, granular temporary plugging agents are pumped in the early stages of the pre-fluid or sand-carrying fluid to seal the natural or artificial fractures in the fault zone, and the scale of fracturing transformation is reduced during fracturing.

2. A comprehensive anti-channeling method for reducing the pressure channeling ratio between wells according to claim 1, characterized in that: Specifically, the fault avoidance is to obtain the location of the fault zone based on 3D seismic and well logging interpretation, and not to perform perforation fracturing within 30 meters of the fault in the fracturing section where the fault and the well intersect.

3. A comprehensive anti-channeling method for reducing the pressure channeling ratio between wells according to claim 1, characterized in that: The specific way to avoid natural fractures is to determine the location of large natural fractures through well logging interpretation, specifically logging blueprint resistance. In the fracturing section where the large fracture and the well intersect, no perforation fracturing is carried out within 20 meters of the large fracture.

4. A comprehensive anti-channeling method for reducing the pressure channeling ratio between wells according to claim 1, characterized in that: In actual construction, if two hydraulic fractures may intersect while expanding along the maximum horizontal principal stress, the perforation and fracturing positions of the fracturing well should be adjusted to avoid the intersection of the two hydraulic fractures and the resulting pressure channeling.

5. A comprehensive anti-channeling method for reducing the pressure channeling ratio between wells according to claim 2 or 3, characterized in that: In areas with water injection wells, horizontal wells shall not be perforated or fractured within 20 meters from the waterline.

6. The comprehensive anti-channeling method for reducing the pressure channeling ratio between wells according to claim 1 is characterized by: In the temporary blocking prevention, the granular temporary blocking agent is DA-2 blocking agent.

7. The comprehensive anti-channeling method for reducing the pressure channeling ratio between wells according to claim 1 is characterized by: During the fracturing process, the wellhead pressure of the adjacent well rises rapidly, so the fracturing construction is stopped and a small-particle temporary plugging agent is pumped with clean water to seal the cracks.

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