Fracture volume multiple method for evaluating the damage degree of drilling and completion fluids in reservoir fractures

Abstract

The present invention discloses a fracture volume multiple method for evaluating the damage degree of drilling and completion fluids in fractured tight reservoirs. In view of the practical problems that the core size is not uniform in the indoor experimental evaluation of drilling and completion fluids in fractured tight reservoirs, the damage degree of reservoir fractures is not related to the experimental invasion amount, and the distinction between the experimental leakage amount and the experimental filtration amount is not high, the damage degree of drilling and completion fluids in reservoir fractures is qualitatively and quantitatively characterized based on the drilling and completion fluid fracture invasion amount and the core fracture volume. The present invention eliminates the influence of indoor core size on experimental results, improves the accuracy of reservoir damage mechanism diagnosis, more objectively evaluates the damage degree of completion fluids in fracture leakage reservoirs, and can simply select or optimize drilling and completion fluids and formulations. At the same time, the experimental filtration amount and the experimental leakage amount are distinguished, which is helpful to evaluate the formation time and strength of the drilling fluid filter cake.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas reservoir damage evaluation, and relates to a method for evaluating the damage degree of drilling and completion fluid reservoirs in fractured reservoirs, which is mainly used to determine the damage degree of drilling and completion fluids to reservoirs. Background Art

[0002] With the exploitation of oil and gas resources, the difficulty of exploitation is increasing. During the drilling and completion process, drilling and completion fluids can easily invade reservoir sections with developed fractures, leading to engineering problems such as reduced production capacity during the production stage. This has seriously affected the oil production process and caused huge economic losses. The main reason is the failure to accurately evaluate the degree of damage to the reservoir caused by drilling and completion fluids.

[0003] It is particularly important to accurately analyze the degree and mechanism of damage to drilling and completion fluids. If the right remedy is not found, it may lead to a reduction in oil and gas production and failure to achieve the target production. In severe cases, it may lead to serious engineering accidents such as serious natural gas leakage that seriously endanger human safety.

[0004] The indoor evaluation method of drilling fluid and completion fluid damage to oil layer (SY / T 6540-2021) is a representative method for evaluating drilling fluid and completion fluid damage to oil layer, but it does not mention how to judge the degree of drilling and completion fluid reservoir damage by leakage. Under laboratory conditions, the degree of drilling and completion fluid reservoir damage to fractured tight reservoirs can be evaluated by using samples such as full-diameter cores and standard small core plungers. During the experiment, different sample sizes resulted in differences in leakage, permeability recovery rate, and pressure bearing capacity. If there is no reasonable calculation method, using conventional methods to evaluate tight reservoirs with developed fractures, the intrusion volume of cores of different sizes varies greatly, which may lead to low accuracy of experimental evaluation or even the opposite experimental conclusion.

[0005] Since fractures are the main flow channels of fractured tight reservoirs, studying the relationship between the amount of drilling and completion fluid invasion and the degree of reservoir damage in fractures of different widths is of great significance for the diagnosis of drilling and completion fluid reservoir mechanism and the optimization of reservoir protection formula. Summary of the invention

[0006] The purpose of the present invention is to provide a method for evaluating the damage degree of drilling and completion fluid in reservoir fractures. The method establishes a damage degree evaluation index for drilling and completion fluid in fractured reservoirs based on the volume multiple of invaded fractures by establishing a relationship between the volume multiple of invaded fractures and the damage degree of reservoirs.

[0007] When drilling into fractured tight reservoirs, the leakage volume and leakage rate are often large. However, in indoor experiments, the drilling fluid may also experience continuous leakage, instantaneous leakage and filtration loss. The reservoir damage evaluation results and invasion volume measurement results are greatly affected by the size of the fracture module used. The invasion volume per unit fracture is calculated based on the instantaneous invasion volume and the cumulative invasion volume, and the invasion volume of the actual drilling process is estimated, and the invasion volume of the indoor experiment is linked to the invasion volume of the actual drilling process.

[0008] In order to achieve the above objectives, the present invention provides the following technical solutions.

[0009] This method can be widely used in fractured tight reservoirs and establishes a new method based on the intrusion fracture volume multiple f pv Characterization of the evaluation method of the damage degree of drilling and completion fluid reservoir. The fracture volume multiple method for evaluating the damage degree of drilling and completion fluid reservoir fractures includes the following steps:

[0010] ①Pre-process the core, measure the core mass m0 and core length L, and calculate the cross-sectional area A of the core fracture;

[0011] ② Under certain temperature and pressure conditions, the drilling and completion fluid contacts the core in reverse and circulates for a certain period of time. The cumulative loss and filtration loss of the drilling and completion fluid within the time t are Q, and the core mass m1 is measured;

[0012] ③ Calculate the experimental intrusion crack volume multiples

[0013] ④ According to the experimental intrusion crack volume multiple f pv , determine the reservoir damage rate D k .

[0014]

[0015] Compared with the existing methods, this method has the following beneficial effects:

[0016] 1. Eliminate the influence of indoor core size on the experimental results, and more objectively evaluate the degree of damage of drilling and completion fluids in fractured and leaky reservoirs. According to the different damage levels evaluated by different cores, this method can unify the experimental results of other types of cores such as long fracture cores, standard plungers, and full-diameter cores, and eliminate the differences in the experiments of cores of different sizes.

[0017] 2. The degree of reservoir damage based on the leakage is more accurate, which is helpful for optimizing the formulation of drilling and completion fluids. In the past, drilling and completion fluid reservoir damage experiments used the permeability recovery rate of the damaged core to characterize the degree of reservoir damage. When the fracture width is large, the drilling and completion fluid cannot be plugged and the permeability recovery rate is high, which is obviously inconsistent with the actual working conditions.

[0018] 3. The experimental filtration and experimental leakage are distinguished, which is helpful to evaluate the formation time and strength of the drilling fluid filter cake. In the past, the experimental filtration and experimental leakage were usually confused. In fact, the experimental leakage is mainly in the process of filter cake formation, while the experimental filtration is the filtration after the filter cake is formed. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, an embodiment of the present invention is further described. The embodiment is only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the content of the present invention also belong to the scope of protection of the present invention.

[0020] Take a well in a typical volcanic rock reservoir as an example. The wellbore structure is three-opening. When drilling to the Shahejie Formation, it encounters a fractured dense volcanic rock reservoir. According to the fracture volume multiple method for evaluating the degree of damage of drilling and completion fluid in reservoir fractures, the experimental steps are as follows:

[0021] ①Pre-process the core, measure the core mass m0 and core length L, and calculate the cross-sectional area A of the core fracture;

[0022] ② Under certain temperature and pressure conditions, the drilling and completion fluid contacts the core in reverse and circulates for a certain period of time. The cumulative intrusion volume of the drilling and completion fluid within the time t is Q, and the core mass m1 is measured;

[0023] ③ Calculate the experimental intrusion crack volume multiples

[0024] ④ According to the experimental intrusion fracture volume multiple, determine the reservoir damage rate D k And the damage range w .

[0025]

[0026] In order to illustrate the feasibility and reliability of this method, this method and the industry standard method were used to evaluate the degree of damage of drilling and completion fluids in this block.

[0027]

[0028] In summary, the present invention can determine the volume multiple of the drilling and completion fluid invading fractures according to the drilling and completion fluid invasion amount, calculate and determine the degree of damage to the drilling and completion fluid reservoir fractures, and provide technical reference and direction for optimizing the drilling fluid.

Claims

1. The fracture volume multiple method for evaluating the degree of reservoir damage of completion fluid is characterized by The steps include: ①Pre-process the core and measure the core mass m0, core length L, completion fluid density ρ w , calculate the cross-sectional area A of the core fracture; ② Under certain temperature and pressure conditions, the completion fluid contacts the core in reverse and circulates for a certain period of time. The cumulative invasion volume of the completion fluid is Q within the time t, and the core mass m1 is measured; ③ Calculate the experimental intrusion crack volume multiples ; ④ According to the experimental intrusion crack volume multiples , determine the reservoir damage rate D k； 。 2. The fracture volume multiple method for evaluating the degree of reservoir damage by completion fluid according to claim 1, characterized in that: The time t is the time from the start of the experiment to the complete elimination of leakage.

3. The fracture volume multiple method for evaluating the degree of reservoir damage by completion fluid according to claim 1, characterized in that: The core is a fracture core, including an artificial fracture core, a Brazilian splitting fracture core, and a 3D printed fracture core.

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