An optimization design method for overall volume fracturing in long vertical well sections

Abstract

The present invention discloses a method for optimizing the overall volume fracturing design of a long vertical well section network, including: optimizing the fracturing layer, the well network type and the well spacing; establishing a new well production model according to the fracturing layer, the well network type and the well spacing; implementing single well construction optimization according to the new well production model, and establishing a set of construction optimization parameter schemes; after optimizing the construction parameters of the construction optimization parameter schemes, performing production prediction, and obtaining the optimal development plan. The method for optimizing the overall volume fracturing design of a long vertical well section network disclosed by the present invention can apply the large-scale volume fracturing technology used in horizontal well development to the reservoir transformation of vertical wells, is suitable for the production improvement transformation of vertical wells in old well areas in multi-layer reservoirs, and is helpful to guide the transformation of old well areas.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to an overall volume fracturing optimization design method for a long vertical well pattern. Background Art

[0002] Large-scale volume fracturing technology is generally used in the development of horizontal wells in shale oil reservoirs. It can form a network of interlaced fractures in tight reservoirs, thereby greatly increasing the scope of transformation. It is rarely used in vertical well areas. Most old well blocks are multi-layer reservoirs. Vertical wells are used to connect and exploit each layer, which has a low recovery rate and a limited area of ​​utilization. When the development effect of old wells is not good and new wells need volume fracturing, how to maximize the production capacity of the old vertical well area under the existing well network conditions and how to apply the current advanced horizontal well integral fracturing technology to the transformation of old vertical well areas have become another research direction for the production increase and transformation of old well areas. Summary of the invention

[0003] The purpose of the present invention is to provide a method for optimizing the overall volume fracturing design of a long vertical well section network. When the development effect of an old well area is not good, a large-scale volume fracturing technology commonly used in horizontal wells is applied to the old vertical well blocks in multi-layer reservoirs. The vertical wells are operated as horizontal wells to transform the vertical well network and improve its development effect. This provides a new idea for the transformation of the vertical well sections in the old area and helps to guide the transformation of the old well area.

[0004] The present invention provides a method for optimizing the design of an overall volume fracturing pattern of a long vertical well section, comprising:

[0005] Optimize fracturing layers, well pattern types and well spacing;

[0006] Establishing a new well production model according to the fracturing layer, the well pattern type and the well spacing;

[0007] Implement single well construction optimization according to the new well production model and establish a set of construction optimization parameter schemes;

[0008] After optimizing the construction parameters of the construction optimization parameter scheme, production prediction is performed to obtain the optimal development plan.

[0009] Specifically, the optimization of fracturing layers, well pattern types and well spacing includes the following steps:

[0010] Step A1: Fracturing layer selection and well pattern spacing determination

[0011] If the original fracturing layer and well pattern spacing of the well area have been determined, optimization can be carried out under the original layer and well pattern spacing conditions; if the fracturing layer is the original main layer of the old well area, the main oil layer and the adjacent layer are selected for fracturing transformation; the fracturing layer is specifically determined by combining oil testing, well testing, well logging and mud logging;

[0012] Step A2: The well pattern type and well spacing should be adjusted on the original basis as much as possible or remain unchanged, or new wells should be added as needed to reduce the well spacing.

[0013] Specifically, establishing the new well production model includes the following steps:

[0014] Step B1: Establish a 3D geological and engineering integrated model

[0015] According to the fracturing layer, well pattern type and well spacing, as well as the geological characteristics of the well area and reservoir properties, combined with geological data, the fracturing software petrel is used to establish a three-dimensional geological engineering integrated model, including fracture distribution, thickness, layer system and grid accuracy. The porosity, oil saturation, horizontal minimum geostress, horizontal maximum geostress and pore pressure are obtained based on the three-dimensional geological engineering integrated model;

[0016] Step B2: Establish a natural fracture model based on the 3D geological engineering integrated model

[0017] The occurrence, dip, density and size of the fractures are obtained based on resistivity imaging logging, and the natural fracture model is established using the fracturing software petrel in combination with porosity, oil saturation, horizontal minimum geostress, horizontal maximum geostress and pore pressure;

[0018] Step B3: Arrange new wells along the extension direction of the fractures on the natural fracture model and establish a new well production model.

[0019] Specifically, establishing a set of the construction optimization parameter scheme includes the following steps:

[0020] Step C1: Apply the control variable method to select the optimal parameter value

[0021] The construction displacement, cluster spacing, sand carrying capacity, fracturing fluid dosage, viscosity and fracturing sequence were selected as single variables, and the control variable method was used to substitute the single variables into the new well production model for numerical simulation to obtain the expansion of cracks under the condition of single variable change.

[0022] Step C2: using the control variable method, on the basis of conventional parameter values ​​in the oil field, by changing a single variable, performing fracture inversion, by comparing the fracture morphology, selecting the optimal morphology as the optimal parameter, wherein the fracture morphology includes fracture length, fracture width and fracture height;

[0023] Step C3: Establish a set of construction optimization parameter solutions according to each optimal parameter, substitute the construction optimization parameter solutions into the new well mining model, apply pressure to the new well mining model, and simulate the production of the new well mining.

[0024] Specifically, the steps of obtaining the optimal development plan include:

[0025] Using the construction parameters of the construction optimization parameter scheme, the fracturing software petrel is used to simulate the production changes of new wells under different construction parameters to obtain the construction parameters with the highest production. The crack expansion under this construction parameter is compared. If the construction parameters with the highest production are the same as the construction parameters with the optimal crack morphology, the optimal parameters are reliable. Otherwise, continue to optimize to confirm the reliability of the optimal parameters, and then select the parameters to obtain the optimal development plan.

[0026] The present invention also provides a device for optimizing the design of the overall volume fracturing of a long vertical well pattern, comprising:

[0027] The first processing unit is used to optimize the fracturing layer, well pattern type and well spacing;

[0028] A second processing unit is used to establish a new well production model according to the fracturing layer, the well pattern type and the well spacing;

[0029] The third processing unit is used to implement single well construction optimization according to the new well production model and establish a set of construction optimization parameter solutions;

[0030] The fourth processing unit is used to optimize the construction parameters of the construction optimization parameter scheme, perform production forecasting, and obtain the optimal development plan.

[0031] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the above method when executed by a processor.

[0032] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the steps of the above method.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention discloses an overall volume fracturing optimization design method for a long straight well section well network, which is applicable to the production improvement and transformation of old well areas in multi-layer reservoirs and the volume fracturing of new and old wells. Under natural fracture conditions, by performing volume fracturing on multi-layer reservoirs with low interlayer spacing, thick layers, and many layers, the reservoir can be interfered with in a favorable manner, the formation energy can be supplemented, and a complex fracture network can be formed. The overall volume fracturing optimization design method for a long straight well section well network disclosed by the present invention can apply the large-scale volume fracturing technology used in horizontal well development to the reservoir transformation of vertical wells, is applicable to the production improvement and transformation of vertical wells in old well areas in multi-layer reservoirs, and is helpful to guide the transformation of old well areas. DETAILED DESCRIPTION

[0035] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0036] Example 1

[0037] Embodiment 1 provides a method for optimizing the design of volumetric fracturing in a long vertical well pattern, comprising the following steps:

[0038] Step A: Optimize fracturing layer location, well pattern type and well spacing

[0039] Step A1: Fracturing layer selection and well pattern spacing determination

[0040] If the original fracturing layer and well pattern spacing of the well area have been determined, optimization can be carried out under the original layer and well pattern spacing conditions; if the fracturing layer is the original main layer of the old well area, the main oil layer and the adjacent layer are selected for fracturing transformation; the fracturing layer is specifically determined by combining oil testing, well testing, well logging and mud logging;

[0041] Due to the exhaustion of formation energy in old well areas, the flow resistance of the main oil layer increases. Selecting the main oil layer and adjacent layers for fracturing transformation can improve permeability and increase oil production efficiency.

[0042] Step A2: The well pattern type and well spacing should be adjusted as much as possible on the original basis or remain unchanged, or new wells should be added as needed to reduce the well spacing;

[0043] Since the well network layout and well spacing in old well areas are mostly mature, most of them are developed using several sets of well networks. Large-scale adjustment of the well network does not conform to actual conditions. Therefore, the well network type and well spacing generally do not change much and can be adjusted on the original basis or without change. Alternatively, new wells can be appropriately added as needed to reduce the well spacing, facilitate overall volume fracturing and improve the transformation effect.

[0044] Step B: Establish a new well production model based on the fracturing layer, well pattern type and well spacing

[0045] Step B1: Establish a 3D geological and engineering integrated model

[0046] According to the fracturing layer, well network type and well spacing, as well as the geological characteristics of the well area and reservoir properties, combined with geological data such as drilling logging, the fracturing software petrel is used to establish a three-dimensional geological engineering integrated model, including fracture distribution, thickness, layer system and grid accuracy. According to the three-dimensional geological engineering integrated model, the parameters such as porosity, oil saturation, horizontal minimum geostress, horizontal maximum geostress, and pore pressure are obtained. Among them, the development of the fracturing software petrel began in 1997 and was realized by a team of programmers, geophysicists, geologists and reservoir engineers. The petrel software is a shared earth model tool that discovers reservoir laws through a common data model. In one application, geophysics, geology, rock physics and production data can be imported and visualized, which is easy for all working group members to access. The petrel software is developed by Schlumberger and is an integrated exploration and development platform centered on three-dimensional geological models. It is a geophysical professional software and has been developed to the 2018 version.

[0047] Step B2: Establish a natural fracture model based on the 3D geological engineering integrated model

[0048] The occurrence, inclination, density and size of the fractures are obtained based on resistivity imaging logging, and the natural fracture model is established using the fracturing software petrel in combination with the porosity, oil saturation, horizontal minimum geostress, horizontal maximum geostress, pore pressure and other parameter values.

[0049] Step B3: Arrange new wells along the extension direction of the fractures on the natural fracture model and establish a new well production model.

[0050] Step C: Implement single well construction optimization according to the new well production model and establish a set of construction optimization parameter solutions;

[0051] Step C1: Apply the control variable method to select the optimal parameter value

[0052] The factors such as operation displacement, cluster spacing, sand carrying capacity, fracturing fluid dosage, viscosity and fracturing sequence were selected as single variables. The control variable method was used to substitute the single variables into the new well production model for numerical simulation, and the expansion of the cracks under the condition of single variable change was obtained.

[0053] The following takes the three parameters of displacement, cluster spacing and sand volume as examples to explain the design method in detail. The design of other parameters can refer to the following control variable method design ideas.

[0054] a. Construction displacement design

[0055] Old wells generally use small liquid volumes, usually no more than 6m 3 / min, new wells use large displacement, generally greater than 10 over 6m 3 / min. Set multiple groups of different displacements and other same parameters to simulate crack propagation and compare the crack propagation conditions.

[0056] b. Cluster spacing design

[0057] According to the thickness of the target layer to be transformed, different cluster spacings but the same other parameters were set for simulation, and the crack extension was compared.

[0058] c. Sand carrying capacity design

[0059] The old wells were simulated with low sand content, and different sand contents but the same other parameters were set to compare the fracture expansion.

[0060] Step C2: Using the control variable method, on the basis of conventional parameter values ​​in the oil field, fracture inversion is performed by changing a single variable, and by comparing the fracture morphology, the optimal morphology is selected as the optimal parameter, wherein the fracture morphology includes fracture length, fracture width and fracture height;

[0061] Step C3: Establish a set of construction optimization parameter solutions according to each optimal parameter, substitute the construction optimization parameter solutions into the new well mining model, apply pressure to the new well mining model, and simulate the production of the new well mining.

[0062] Step D: After optimizing the construction parameters of the construction optimization parameter scheme, the production forecast is carried out to obtain the optimal development plan.

[0063] Using the construction parameters of the construction optimization parameter scheme, the fracturing software petrel is used to simulate the production changes of new wells under different construction parameters to obtain the construction parameters with the highest production. The crack expansion under this construction parameter is compared. If the construction parameters with the highest production are the same as the construction parameters with the optimal crack morphology, the optimal parameters are reliable. Otherwise, continue to optimize to confirm the reliability of the optimal parameters, and then select the parameters to obtain the optimal development plan.

[0064] In order to observe the optimization effect more intuitively, the optimal development plan is simulated using the fracturing software petrel, and the simulation days are recommended to be greater than 180 days. The simulation effect can be compared with previous production data to predict the degree of production increase.

[0065] The principles of this method are:

[0066] When renovating old wells, it is necessary to follow the on-site principle of small displacement and high sand ratio;

[0067] Principle of achieving the best transformation volume: Volume fracturing takes the best and largest transformation volume of the entire block as the research goal;

[0068] Principle of reasonable and full utilization of energy: fully and reasonably maximize the utilization of single-layer or multi-layer system energy;

[0069] The original setting is the main principle: the well pattern type of the fracturing layer remains basically unchanged or has little change;

[0070] Control variable principle: Each parameter is optimized using the control variable method.

[0071] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for optimizing the design of volumetric fracturing for a long vertical well pattern, characterized in that: include: Step A: Optimizing the fracturing layer, well pattern type and well spacing, including the following steps: Step A1: Fracturing layer selection and well pattern spacing determination If the original fracturing layer and well pattern spacing of the well area have been determined, optimization can be carried out under the original layer and well pattern spacing conditions; if the fracturing layer is the original main layer of the old well area, the main oil layer and adjacent layers are selected for fracturing transformation; the fracturing layer is specifically determined in combination with oil testing, well testing, well logging and mud logging; Step A2: The well pattern type and well spacing should be adjusted as much as possible on the original basis or remain unchanged, or new wells should be added as needed to reduce the well spacing; Step B: Establishing a new well production model according to the fracturing layer, the well pattern type and the well spacing, including the following steps: Step B1: Establish a 3D geological and engineering integrated model According to the fracturing layer, well pattern type and well spacing, as well as the geological characteristics of the well area and reservoir properties, combined with geological data, the fracturing software petrel is used to establish a three-dimensional geological engineering integrated model, including fracture distribution, thickness, layer system and grid accuracy. The porosity, oil saturation, horizontal minimum geostress, horizontal maximum geostress and pore pressure are obtained based on the three-dimensional geological engineering integrated model; Step B2: Establish a natural fracture model based on the 3D geological engineering integrated model The occurrence, dip, density and size of the fractures are obtained based on resistivity imaging logging, and the natural fracture model is established using the fracturing software petrel in combination with porosity, oil saturation, horizontal minimum geostress, horizontal maximum geostress and pore pressure; Step B3: Arrange new wells along the extension direction of the fractures on the natural fracture model and establish a new well production model; Step C: Implementing single well construction optimization according to the new well production model and establishing a set of construction optimization parameter schemes, including the following steps: Step C1: Apply the control variable method to select the optimal parameter value The construction displacement, cluster spacing, sand carrying capacity, fracturing fluid dosage, viscosity and fracturing sequence were selected as single variables, and the control variable method was used to substitute the single variables into the new well production model for numerical simulation to obtain the expansion of cracks under the condition of single variable change. Step C2: using the control variable method, on the basis of conventional parameter values ​​in the oil field, by changing a single variable, performing fracture inversion, by comparing the fracture morphology, selecting the case with the best morphology as the optimal parameter, wherein the fracture morphology includes fracture length, fracture width and fracture height; Step C3: Establish a set of construction optimization parameter schemes according to each optimal parameter, substitute the construction optimization parameter schemes into the new well mining model, apply pressure to the new well mining model, and simulate the production of the new well mining; After optimizing the construction parameters of the construction optimization parameter scheme, production prediction is performed to obtain the optimal development plan.

2. The method for optimizing the design of the overall volume fracturing of a long vertical well pattern according to claim 1, characterized in that: The steps of obtaining the optimal development solution include: Using the construction parameters of the construction optimization parameter scheme, the fracturing software petrel is used to simulate the production changes of new wells under different construction parameters to obtain the construction parameters with the highest production. The crack expansion under this construction parameter is compared. If the construction parameters with the highest production are the same as the construction parameters with the optimal crack morphology, the optimal parameters are reliable. Otherwise, continue to optimize to confirm the reliability of the optimal parameters, and then select the parameters to obtain the optimal development plan.

3. A device for optimizing the design of the overall volume fracturing of a long vertical well pattern according to claim 1 or 2, characterized in that: include The first processing unit is used to optimize the fracturing layer, well pattern type and well spacing; A second processing unit is used to establish a new well production model according to the fracturing layer, the well pattern type and the well spacing; The third processing unit is used to implement single well construction optimization according to the new well production model and establish a set of construction optimization parameter solutions; The fourth processing unit is used to optimize the construction parameters of the construction optimization parameter scheme, perform production forecasting, and obtain the optimal development plan.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 2 are implemented.

5. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 2 are implemented.