CN111734382B - Method for explaining multiple parameters by testing fracturing through stepped displacement reduction - Google Patents

Method for explaining multiple parameters by testing fracturing through stepped displacement reduction Download PDF

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CN111734382B
CN111734382B CN202010778306.5A CN202010778306A CN111734382B CN 111734382 B CN111734382 B CN 111734382B CN 202010778306 A CN202010778306 A CN 202010778306A CN 111734382 B CN111734382 B CN 111734382B
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pressure
fracturing
displacement
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hole
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CN111734382A (en
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胡永全
王磊
赵金洲
柳博莹
赵超能
王强
傅成浩
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Southwest Petroleum University
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces

Abstract

The invention discloses a method for explaining multiple parameters by testing fracturing with stepped displacement reduction, which comprises the following steps of: s1: testing the change of the bottom-hole pressure in the fracturing construction process by combining a pressure gauge arranged at the bottom of the fracturing string before construction, and selecting the bottom-hole pressure and the injection displacement corresponding to the step descent point in the displacement reduction stage of the fracturing construction; s2: establishing a mechanical balance model of bottom hole pressure, hole friction resistance pressure drop and near-well bending friction resistance pressure drop according to the bottom hole pressure and the injection displacement; s3: substituting the data collected in the step S1 into the mechanical balance model to construct a model solution equation set; s4: and solving the unknown numbers in the equation system by solving the model to obtain the multi-parameter result. The invention can simultaneously obtain accurate fracture closure pressure, perforation hole friction coefficient and near-well bending friction coefficient.

Description

Method for explaining multiple parameters by testing fracturing through stepped displacement reduction
Technical Field
The invention relates to the technical field of hydraulic fracturing, in particular to a method for explaining multiple parameters by testing fracturing through stepped displacement reduction.
Background
A great revolution is taking place in the field of exploration and development of the oil and gas industry worldwide, continuing to extend from conventional oil and gas development to unconventional reservoir oil and gas development. Low permeability, unconventional oil and gas are constantly increasing in global oil and gas production rates, and the oil and gas production rates obtained therefrom are rapidly increasing. However, these reservoirs have low permeability and compactness, a single well generally has no natural capacity, commercial exploitation can be realized only by a certain technical means, and hydraulic fracturing plays an important role in improving the permeability of the reservoir, and can meet the reasonable and efficient transformation requirements of unconventional reservoirs. The fracturing design needs to accurately reflect the data of reservoir properties, fracture characteristics and fracturing fluid properties, and the accuracy of data has great influence on the fracturing construction effect. Accurate reservoir parameters can be obtained by utilizing the test fracturing, so the test fracturing is often carried out before the main fracturing construction to improve the knowledge of the reservoir, and the construction task of the main fracturing is conveniently and successfully completed.
In fracturing construction, especially in inclined shaft fracturing, a near wellbore effect is often generated due to the influences of insufficient hole number, bent cracks, improper perforation positions and the like, and high friction loss of a near wellbore occurs. The high friction resistance not only brings high pumping pressure for construction, but also narrows the seam width at the near well position due to the increase of net pressure, and increases the possibility of early sand removal and well plugging in construction. It is essential to recognize and prevent the adverse effects of the near wellbore piping effect on the construction, of which the hole friction and near wellbore bending friction are the most important. The friction calculation of the perforation mostly adopts the traditional calculation formula, but the flow coefficient of the perforation measured by indoor tests has larger difference with site construction data, and the result obtained by the calculation formula can not be applied to site construction (Zhangjie, Wangyongqing, Chao Shuanglong. friction change research of the perforation in the process of current-limiting fracturing [ J ] petrochemical technology, 2015,22(01): 120-. Bending friction resistance can generally obtain results by using test fracturing, but under the condition of supposing known formation closing pressure, the bending friction resistance of a near-well fracture is explained, and the accuracy of the closing pressure seriously influences the accuracy of the explanation result. The method for analyzing the pressure drop curve after the pump is stopped can explain the conditions of the fractured fracture and the stratum, but the field application of the method is limited due to the requirement of recording long testing time, and the assumed conditions of the method are too ideal and are different from the actual conditions of the stratum. Therefore, a method capable of accurately calculating fracturing multiparameters is needed.
Disclosure of Invention
In view of the above problems, the present invention aims to provide a method for explaining multiple parameters by a step-size-reduction test fracturing, which utilizes a volume-reduction test which is most easily obtained on site and most directly reflects fracturing pressure to simultaneously obtain fracture closure pressure, perforation friction coefficient and near-well bending friction coefficient by analysis. On one hand, the quantity of parameters explained by utilizing the step-down displacement test data is large, the application range of the step-down displacement test fracturing data is enriched, the test fracturing procedure special for determining the fracture closure pressure is saved, the cost is saved, on the other hand, the explained closure pressure is used for replacing the assumed closure pressure for explanation, and therefore the explanation precision of the friction resistance of the hydraulic fracturing perforation hole and the bending friction resistance of the near well is improved. Provides more accurate and effective reference and guidance for subsequent fracturing adjustment or evaluation.
The technical scheme of the invention is as follows:
a method for explaining multiple parameters by testing fracturing in a stepped displacement reduction mode determines multiple parameters by utilizing bottom hole pressure and injection displacement data of a displacement reduction stage in a fracturing process, wherein the multiple parameters comprise fracture closing pressure, a friction coefficient of a perforation hole and a bending friction coefficient of a near well. The method specifically comprises the following steps:
s1: testing the change of the bottom-hole pressure in the fracturing construction process by combining a pressure gauge arranged at the bottom of the fracturing string before construction, and selecting the bottom-hole pressure and the injection displacement corresponding to the step descent point in the displacement reduction stage of the fracturing construction;
s2: establishing a mechanical balance model of bottom hole pressure, hole friction resistance pressure drop and near-well bending friction resistance pressure drop according to the bottom hole pressure and the injection displacement;
s3: substituting the data collected in the step S1 into the mechanical balance model to construct a model solution equation set;
s4: and solving the unknown numbers in the equation system by solving the model to obtain the multi-parameter result.
Preferably, the construction pressure mechanical balance model is as follows:
Pi-Pc＝KpQ2+KnwQ0.5 (1)
in the formula:
Pifor bottom hole pressure in fracturing operationForce, MPa;
Pcthe fracture closure pressure, MPa;
Kpthe coefficient of friction resistance of the perforation hole is dimensionless;
q is the injection displacement, m3/min；
KnwThe coefficient of the near-well bending friction resistance is dimensionless.
Preferably, the system of equations for solving the model is as follows:
Figure GDA0003013767630000021
in the formula:
Q1、Qm、QNrespectively the injection displacement of the first step-down point, the mth step-down point and the Nth step-down point, m3/min；
P1、Pm、PNThe bottom hole pressure in the fracturing construction process of the first step descending point, the mth step descending point and the Nth step descending point is respectively MPa.
Preferably, the solving method of the model solving equation set comprises the following steps:
constructing a function:
y＝Pi＝f(Kp,Knw,Pc)＝KpQ2+KnwQ0.5+Pc (3)
the squared error function is then:
Figure GDA0003013767630000031
performing partial derivation on each variable of the error square function to construct a new three unknown numbers (K)p、Knw、Pc) And simultaneously solving the equation sets of the three equations to obtain the multi-parameter result.
Preferably, to minimize the error, the partial derivative for each variable is made equal to 0.
Compared with the prior art, the invention has the following advantages:
the method combines the influences of the friction resistance of the fracturing perforation hole and the bending friction resistance of the near well, utilizes the test data of the displacement reduction stage in the fracturing which is most easily carried out on site and most directly reflects the change condition of the bottom hole pressure, can simultaneously obtain the friction resistance coefficients of the shaft and the hole, the fracture closing pressure and other parameters through analysis, and does not need to carry out special closing pressure test. The method not only can save additional fracturing testing steps and test cost, but also can make full use of test data, improve the accuracy and reliability of interpretation results, and provide a basis and a method for diagnosing the fractured fractures for development technicians.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic view of a third construction curve according to example 1 of the present invention;
FIG. 2 is a schematic view of a fourth construction curve according to embodiment 1 of the present invention;
FIG. 3 is a graph showing the results of comparing the friction coefficient of the eyelet according to example 1 of the present invention with that of the conventional method;
FIG. 4 is a graph showing the comparison result between the friction coefficient of the near well and the conventional method in example 1 of the present invention;
FIG. 5 is a graph illustrating the results of comparing the fracture closure pressure according to example 1 of the present invention with that of the conventional method.
Detailed Description
The invention is further illustrated with reference to the following figures and examples. It should be noted that, in the present application, the embodiments and the technical features of the embodiments may be combined with each other without conflict. Unless defined otherwise, technical or scientific terms used in the present disclosure should have the ordinary meaning as understood by those of ordinary skill in the art to which the present disclosure belongs. The use of the terms "comprising" or "including" and the like in the present disclosure is intended to mean that the elements or items listed before the term cover the elements or items listed after the term and their equivalents, but not to exclude other elements or items.
Example 1
A method for interpreting multiple parameters by a step-and-drop displacement test fracturing comprises the following steps:
firstly, collecting the variation data of the bottom pressure in the fracturing construction process, the injection displacement of a step-down point in the displacement reduction stage, and obtaining rock mechanical parameters according to field logging information, wherein the rock mechanical parameters are used for verifying the invention by adopting a well-closing pressure decreasing curve testing method in the follow-up process.
And secondly, selecting the bottom hole pressure and the injection displacement corresponding to the step descent point in the fracturing construction displacement reduction stage in the collected data.
The Young's modulus of the target reservoir of the XJ oilfield A086 well is 10GPa, and the Poisson ratio is 0.27. The crude oil viscosity was 4.7 mPas, the depth of the middle was 640m and the fracturing fluid viscosity was 3 mPas under formation conditions. The staged fracturing of the horizontal well is implemented, the testing fracturing is carried out on the third stage and the fourth stage, the testing fracturing construction data curve is shown in the figure 1 and the figure 2, and the bottom hole pressure and the injection displacement of the data point at the displacement reduction stage are obtained and are shown in the table 1:
TABLE 1 bottom hole pressure and injection Displacement during drawdown phase
Figure GDA0003013767630000041
Then, the collected data is substituted into the construction pressure mechanical balance model shown in the formula (1), and a model solution equation set shown in the formula (2) is constructed.
Finally, the unknowns in equation (2) are solved, and the solving result is shown in table 2:
TABLE 2 solving results of the model solving equations
Figure GDA0003013767630000042
Figure GDA0003013767630000051
The multi-parameter results of the present invention interpretation are compared to the displacement reduction interpretation and G-function interpretation methods, and the comparison results are shown in fig. 3-5. As can be seen from the table 2 and the figures 3-5, the solving result of the method is similar to the traditional explaining result, the friction coefficient error of the hole is not more than 0.06, the bending friction coefficient error of the near well is not more than 0.8, and the fracture closing pressure error is not more than 0.6MPa, so that the method is reliable in result, and can provide effective reference and guidance for the fracturing adjustment or evaluation of other wells.
In addition, the invention has prominent substantive features and significant progress compared with the displacement reduction interpretation. The reduced displacement interpretation is that K is obtained by obtaining data points in a reduced displacement stage and fittingpAnd KnwHowever, the difference of the present invention is that the data points selected in the conventional method must include the pressure corresponding to the displacement of 0, and the field data shows that the bottom hole pressure fluctuation at the instant pump-stopping stage is large, so that the accurate instant pump-stopping pressure cannot be obtained. In addition, the present invention can obtain the crack closure pressure value in addition to Kp and Knw.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (4)

1. A method for explaining multiple parameters by testing fracturing in a stepped displacement reduction manner is characterized in that the multiple parameters are determined by utilizing bottom hole pressure and injection displacement data of a displacement reduction stage in the fracturing process, wherein the multiple parameters comprise fracture closing pressure, perforation hole friction coefficient and near-well bending friction coefficient; the determining the multi-parameter specifically comprises the following steps:
s1: testing the change of the bottom-hole pressure in the fracturing construction process by combining a pressure gauge arranged at the bottom of the fracturing string before construction, and selecting the bottom-hole pressure and the injection displacement corresponding to the step descent point in the displacement reduction stage of the fracturing construction;
s2: establishing a mechanical balance model of bottom hole pressure, hole friction resistance pressure drop and near-well bending friction resistance pressure drop according to the bottom hole pressure and the injection displacement; the mechanical balance model is as follows:
Pi-Pc＝KpQ2+KnwQ0.5 (1)
in the formula:
Pithe bottom hole pressure in the fracturing construction process is MPa;
Pcthe fracture closure pressure, MPa;
Kpthe coefficient of friction resistance of the perforation hole is dimensionless;
q is the injection displacement, m3/min；
KnwThe coefficient of the near-well bending friction resistance is dimensionless;
s3: substituting the data collected in the step S1 into the mechanical balance model to construct a model solution equation set;
s4: and solving the unknown numbers in the equation system by solving the model to obtain the multi-parameter result.
2. The method for interpreting multiparameters for a stepped-displacement test fracture as claimed in claim 1, wherein the model solves the system of equations as:
Figure FDA0003029627670000011
in the formula:
Q1、Qm、QNrespectively the injection displacement of the first step-down point, the mth step-down point and the Nth step-down point, m3/min；
P1、Pm、PNThe bottom hole pressure in the fracturing construction process of the first step descending point, the mth step descending point and the Nth step descending point is respectively MPa.
3. The method for interpreting multiparameters in a stepped-displacement test fracture according to claim 2, wherein the method for solving the model to solve the system of equations comprises the following steps:
constructing a function:
y＝Pi＝f(Kp,Knw,Pc)＝KpQ2+KnwQ0.5+Pc (3)
the squared error function is then:
Figure FDA0003029627670000021
and (3) performing partial derivation on each variable of the error square function, constructing a new equation set containing three unknown numbers and three equations, and performing simultaneous solution to obtain the multi-parameter result.
4. The method for interpreting multiparameters according to claim 3, wherein, to minimize the error, the partial derivative for each variable is made equal to 0.
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Publication number Priority date Publication date Assignee Title
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RU2565617C1 (en) * 2014-10-13 2015-10-20 Открытое акционерное общество "Татнефть" имени В.Д. Шашина Method of development of sandwich-type oil pool using hydraulic fracturing
CN107476790A (en) * 2016-06-07 2017-12-15 中国石油化工股份有限公司 A kind of fracturing process for the unlimited discharge capacity of pressure limiting for improving shale gas crack transformation volume
CN108829945A (en) * 2018-05-29 2018-11-16 西南石油大学 One kind assessing storey increase design volume method based on Fracturing Pressure in real time
CN110984949A (en) * 2020-01-02 2020-04-10 中国石油集团川庆钻探工程有限公司 Shale continuous sand-adding fracturing process

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Publication number Priority date Publication date Assignee Title
RU2565617C1 (en) * 2014-10-13 2015-10-20 Открытое акционерное общество "Татнефть" имени В.Д. Шашина Method of development of sandwich-type oil pool using hydraulic fracturing
CN104533375A (en) * 2014-12-26 2015-04-22 中国石油天然气股份有限公司 Natural fractured reservoir fracturing reformation method
CN107476790A (en) * 2016-06-07 2017-12-15 中国石油化工股份有限公司 A kind of fracturing process for the unlimited discharge capacity of pressure limiting for improving shale gas crack transformation volume
CN108829945A (en) * 2018-05-29 2018-11-16 西南石油大学 One kind assessing storey increase design volume method based on Fracturing Pressure in real time
CN110984949A (en) * 2020-01-02 2020-04-10 中国石油集团川庆钻探工程有限公司 Shale continuous sand-adding fracturing process

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