CN106089191B - Method for identifying pressure fracture zone structure well logging - Google Patents

Abstract

The invention relates to a well logging identification method for a pressure fracture zone structure, which is characterized by analyzing a pressure stress environment, selecting a target drilling and well logging curve, calculating fracture sensitivity parameters, carrying out normalization calculation on all parameters and constructing a comprehensive judgment parameter FZI of the internal structure of a fracture zone. The method can effectively utilize logging information to identify the internal structure of the fracture zone, and the selected curve type is conventional standard logging, so that the method has strong operability.

Description

A logging identification method of compressive fault zone structure

technical field

The invention belongs to the technical field of oil and natural gas exploration and development, and particularly relates to a logging identification method for a compressive fault zone structure.

Background technique

Faults are developed in the oil-gas-bearing areas, and the faults control the migration and accumulation of oil and gas. Fracture is a tectonic deformation phenomenon in which the rock layer ruptures under the action of stress and produces obvious relative movement along the rupture surface. During the dislocation process, the rock layers on both sides of the fracture surface are squeezed and ground, and the rock is severely broken. At the same time, a large number of fractures associated with the fault are generated on both sides (Song et al., 2010). Zhang Qinglian et al. (2010) found through field measurements that the density of fault-controlled tectonic fractures has an exponentially decreasing relationship with the distance from the fault, and the closer to the fracture surface, the more developed the fracture. Billi A (2003) divided this fault structure into two parts: the fault core and the fractured zone. The fault core is a narrow zone composed of the main slip surface and fault rocks; the fractured zone is located on the periphery of the fault core and is mainly composed of fracture development zones and Small fault composition (Agosta F et al, 2006). Tveranger J (2005), Braathen A (2009), etc. defined the three-dimensional space of the rock affected by the fault as a fault envelope, including two parts: the fracture zone and the induced fracture zone. Fractures are the main feature, and various types of induced fractures are mainly developed in the induced fracture zone (Fu Xiaofei et al., 2005). In short, a fault is not a simple "surface", but a "belt" (Fu Guang et al., 2008), with a complex internal structure (Caine, 1996; Gudmundsson A, 2001; Fu Xiaofei et al., 2005). Wu Zhiping (2010) divided the fault zone into two types of structural units: sliding fracture zone and induced fracture zone according to the degree of deformation.

A compressive fracture is a reverse fault formed under the action of a compressive stress field. Its strong force, severe rock fragmentation along both sides of the sliding surface, complete fault zone structure, and obvious control of oil and gas accumulation, are the key factors for oil and gas migration and accumulation in the western basins of my country. Usually, the rock in the sliding fracture zone of the compressive fault zone is severely broken and is in the form of rock powder, mostly fault gouges, partly mylonitized, poor fluid passing capacity, and strong sealing ability for oil and gas (Wu Kongyou et al., 2012). ). In the induced fracture zone, a large number of fractures are developed, and the fluid passing ability is strong, which provides a channel for oil and gas migration (Fu Xiaofei et al., 2005). In short, the fault zone has the dual capacity of transporting and sealing oil and gas. That is, the temporal and spatial differences in the internal structure of the fault zone will cause it to play different roles in the process of hydrocarbon migration and accumulation. Therefore, predicting the structural characteristics of fault zones developed in the deep underground of oil and gas areas is of great significance to the exploration of oil and gas reservoirs.

As for the compressive fault in the coverage area, because it cannot be directly observed, how to accurately identify the fault structure has always been one of the difficult problems in petroleum geological exploration. Liu Wei et al. (2013) proposed to use four parameters of resistivity difference ratio, porosity ratio, curve change rate and well diameter increase rate, combined with principal component analysis method to quantitatively identify the internal structure of the fault zone. However, this method cannot effectively identify the internal structure of the fault zone during the application process due to the few parameters selected and the lack of consideration of the variation range of the curve. Zhao Yonggang et al. (2013) proposed eight parameters: three porosity ratio, equivalent elastic modulus difference ratio, secondary porosity, double induction amplitude difference index, crack coefficient, relative abnormality of well diameter, resistivity invasion correction and cementation index It is an effective parameter for judging the development of fractures in the formation. From the characteristics of the induced fracture zone and the sliding fracture zone inside the fault zone, it can be seen that the development of fractures is one of the important differences between the two structures. Therefore, selecting the fracture sensitivity index and constructing the comprehensive discriminating parameter of the fault structure can be obtained from the logging curve. Effectively judge the internal structure of the fault zone.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a logging identification method for the structure of a compressive fault zone. Through multi-parameter logging curve fitting, a comprehensive judgment parameter of the fault zone structure is constructed, and combined with the characteristics of the internal structure of the fault zone, the compressive capacity of the coverage area can be quantitatively divided. The internal structure of faults provides technical support for accurately evaluating the opening and closing properties of faults and improving the effectiveness of oil and gas exploration and prediction.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions to be realized:

A logging identification method for a compressive fault zone structure, comprising the following steps:

(1) Judging whether the stress environment in the work area is a compressive stress environment, if it is a compressive stress environment, go to step (2);

(2) Select and calculate the fracture sensitivity parameters: ①The ratio of deep and shallow resistivity difference R _TC , ②Three porosity logging, ③Curve change rate, ④Well diameter increase rate CAL _d

①Resistivity difference ratio R _TC :

Among them, R _D is the deep lateral logging value or deep resistivity logging value, and R _S is the shallow lateral logging value or shallow resistivity logging value; obtain the curve F( _RTC )

②Three porosity logging

The three porosity logging curves include Acoustic Time Difference (AC), Density (DEN) and Compensated Neutron (CNL); among them, the porosity calculated by the Acoustic Time Difference is the primary porosity, and the porosity calculated by using the density and the compensated neutron is Total porosity including at least secondary porosity of fractures and dissolution pores;

The formula for calculating the primary porosity of the acoustic time difference is:

Among them, Δt is the sonic time difference value of the formation read from the sonic time difference curve, Δt _f is the sonic time difference value of the fluid in the pores, and Δt _ma is the sonic time difference value of the rock skeleton;

The formula for calculating total porosity from density logging is:

Among them, ρ _b is the measured value read out from the density log curve, ρ _f is the density value of the fluid in the pores, and ρ _ma is the rock skeleton density value;

The formula for calculating total porosity from compensated neutron logging is:

in, To compensate for the measured value read on the neutron curve, is the neutron value of the rock skeleton, is the neutron value of the fluid in the pores;

total porosity value

Changes in secondary porosity caused by factors such as fractures

③The rate of change of the curve

Select the curve sensitive to cracks with acoustic transit time (AC), compensated neutron (CNL) and density (DEN) to calculate the curve change rate. The calculation formula is:

ΔX _i =(|X _i-1 -X _i |+|X _i+1 -X _i |)/X _i

Among them, X _i is the logging curve value of the current depth point, and X _i-1 and X _i+1 are the logging curve values of two points adjacent to the current depth point;

④ Well diameter increase rate CAL _d

The calculation formula is:

CAL is the drill bit diameter, CAL _J is the measured well diameter;

(3) Perform normalization calculation for each parameter.

The curve (AC, CNL) change rate, three porosity, and well diameter increase rate are normalized by the following formula:

Y=(XX _min )/(X _max -X _min )

Among them, X represents the curve (AC, CNL) change rate, three porosity or the actual measurement value of the well diameter increase rate, X _max represents the curve (AC, CNL) change rate, three porosity or well diameter increase rate of this kind of logging curve The maximum measured value of the increase rate, X _min represents the curve (AC, CNL) change rate of this kind of logging curve, and the minimum measured value of the three porosity or well diameter increase rate; the curves F(ΔAC), F(ΔCNL), F(ΔCAL _d ), F(ΔΦ _P );

The density (DEN) rate of change is normalized using the following formula:

Y=1-(XX _min )/(X _max -X _min );

Among them, X represents the measured value of density logging, X _max represents the maximum measured value of density logging, and X _min represents the minimum measured value of density logging; the curve F(ΔDEN) is obtained;

(4) Constructing the comprehensive discriminating parameter FZI of the internal structure of the fault zone

FZI=[F(ΔAC)+F(ΔCNL)+F(ΔDEN)+F(R _TC )+F(ΔCAL _d )+F(ΔΦ _P )]/6

Among them, F is a function relative to various curves, which satisfies the following conditions:

In the formula, x represents ΔAC, ΔCNL, ΔDEN, R _TC , ΔCAL _d or ΔΦ _P , a and b are abnormal critical values, and a<b.

The advantages and positive effects of the present invention are: the present invention can effectively use logging data to identify the internal structure of the fault zone, and the selected curve type is conventional standard logging, which has strong operability. Compared with the prior art (qualitatively using a single curve change trend to divide the fault zone structure), it is more convincing to quantify the process of logging curve identification of the internal structure of the fault zone. The study of fault controlling reservoir is of great significance. The invention uses the core observation and imaging logging data to test the identification scheme, and finds that the division is consistent with the core and imaging logging data, which verifies the accuracy of the method.

Other features and advantages of the present invention will become more apparent upon reading the detailed description of the embodiments of the present invention in conjunction with the accompanying drawings.

Description of drawings

FIG. 1 is an implementation roadmap of a specific embodiment of the present invention.

Fig. 2 is a comprehensive diagram of quantitative identification of the log curve of the internal structure of the fault in Well Pai 66.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in Figure 1, analyze the tectonic stress field to determine whether the stress environment in the work area is a compressive stress environment. If it is a compressive stress environment, continue with the following steps.

The target drilling is selected, the logging curve is screened, and the abnormal values a and b of the curve are determined.

Selection and calculation of fracture sensitivity parameters: ① deep-shallow resistivity difference ratio R _TC , ② three porosity logging, ③ curve change rate, ④ well diameter increase rate CAL _d

①Resistivity difference ratio R _TC :

Among them, R _D is the deep lateral logging value or deep resistivity logging value, and R _S is the shallow lateral logging value or shallow resistivity logging value; the curve F( _RTC ) is obtained;

②Three porosity logging

The three porosity logging curves include Acoustic Time Difference (AC), Density (DEN) and Compensated Neutron (CNL); among them, the porosity calculated by the Acoustic Time Difference is the primary porosity, and the porosity calculated by using the density and the compensated neutron is Total porosity including at least secondary porosity of fractures and dissolution pores;

The formula for calculating the primary porosity of the acoustic time difference is:

Among them, Δt is the sonic time difference value of the formation read from the sonic time difference curve, Δt _f is the sonic time difference value of the fluid in the pores, and Δt _ma is the sonic time difference value of the rock skeleton;

The formula for calculating total porosity from density logging is:

Among them, ρ _b is the measured value read out from the density log curve, ρ _f is the density value of the fluid in the pores, and ρ _ma is the rock skeleton density value;

The formula for calculating total porosity from compensated neutron logging is:

in, To compensate for the measured value read on the neutron curve, is the neutron value of the rock skeleton, is the neutron value of the fluid in the pores;

total porosity value

Changes in secondary porosity caused by factors such as fractures

③The rate of change of the curve

Select the curve sensitive to cracks with acoustic transit time (AC), compensated neutron (CNL) and density (DEN) to calculate the curve change rate. The calculation formula is:

ΔX _i =(|X _i-1 -X _i |+|X _i+1 -X _i |)/X _i

Among them, X _i is the logging curve value of the current depth point, and X _i-1 and X _i+1 are the logging curve values of two points adjacent to the current depth point;

④ Well diameter increase rate CAL _d

The calculation formula is:

CAL is the drill bit diameter, CAL _J is the measured well diameter;

(3) Perform normalization calculation for each parameter.

The curve (AC, CNL) change rate, three porosity, and well diameter increase rate are normalized by the following formula:

Y=(XX _min )/(X _max -X _min )

Among them, X represents the curve (AC, CNL) change rate, three porosity or the actual measurement value of the well diameter increase rate, X _max represents the curve (AC, CNL) change rate, three porosity or well diameter increase rate of this kind of logging curve The maximum measured value of the increase rate, X _min represents the curve (AC, CNL) change rate of this kind of logging curve, and the minimum measured value of the three porosity or well diameter increase rate; the curves F(ΔAC), F(ΔCNL), F(ΔCAL _d ), F(ΔΦ _P );

The density (DEN) rate of change is normalized using the following formula:

Y=1-(XX _min )/(X _max -X _min );

Among them, X represents the measured value of density logging, X _max represents the maximum measured value of density logging, and X _min represents the minimum measured value of density logging; the curve F(ΔDEN) is obtained;

(4) Constructing the comprehensive discriminating parameter FZI of the internal structure of the fault zone

FZI=[F(ΔAC)+F(ΔCNL)+F(ΔDEN)+F(R _TC )+F(ΔCAL _d )+F(ΔΦ _P )]/6

Among them, F is a function relative to various curves, which satisfies the following conditions:

In the formula, x represents ΔAC, ΔCNL, ΔDEN, R _TC , ΔCAL _d or ΔΦ _P , a and b are abnormal critical values, and a<b.

This method has achieved good experimental results in the experiment on the northwestern margin of the Junggar Basin. The Junggar Basin is an important hydrocarbon-bearing basin in western my country. It has experienced tectonic movements from the Hercynian to the Himalayas, and has developed compressive faults. The faults have been active for a long time, have a long horizontal extension distance, and have a large vertical fault throw. Some wells drilled through the fault zone. This method was used to identify the internal structure of the fault zone in Well Pai 66 drilled through the Hongche fault zone, and the effect was good (Fig. 2). The Hongche fault zone in this well can be divided into three parts: the induced fracture zone in the hanging wall, the sliding fracture zone and the induced fracture zone in the foot wall. Compared with the two-disk induced fracture zone, the R _TC value of the sliding fracture zone is negative or zero, indicating that the fracture is not developed; the CAL _d value is obviously small and relatively stable, indicating that the degree of well caliber collapse is weaker than that of the induced fracture zone; ΔDEN is relatively stable , but the induced fracture zones on both sides have obvious changes; ΔAC and ΔCNL are small and change little, but the induced fracture zones have obvious jumps; Φ _P is stable, which is related to the overall lithology of mudstone; FZI It shows a significantly low value, indicating that the fractures are not developed in the sliding fracture zone as a whole, but the fractures are obviously developed in the induced fracture zone.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be The technical solutions described in the foregoing embodiments are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (1)

1. A method for identifying a pressure fracture band structure by logging is characterized by comprising the following steps:

(1) judging whether the stress environment of the work area is a compressive stress environment, and if so, entering the step (2);

(2) selecting and calculating crack sensitivity parameter ① depth resistivity difference ratio R_TC② three-porosity logging, ③ curve change rate, ④ hole diameter increasing rate CAL_d；

① depth resistivity difference ratio R_TC：

Wherein R is_DFor deep lateral or deep resistivity logs, R_sShallow lateral log values or shallow resistivity log values; curve F (R) is obtained_TC)；

② three-porosity logging

The three-porosity log includes acoustic time difference (AC), Density (DEN) and Compensated Neutrons (CNL); wherein, the porosity calculated by using the acoustic wave time difference is primary porosity, and the porosity calculated by using the density and the compensation neutrons is total porosity at least including secondary porosity of cracks and corrosion pores;

the formula for calculating the native porosity by the acoustic time difference is as follows:

wherein, Δ t is the time difference of the formation acoustic wave read from the acoustic time difference curve, Δ t_fIs the difference in acoustic time, Δ t, of the fluid in the pore_maThe acoustic wave time difference value of the rock skeleton is obtained;

the density logging calculates the total porosity as:

where ρ is_bMeasured values, p, read for density logs_fIs the density value of the fluid in the pores, p_maThe density value of the rock skeleton is obtained;

the formula for calculating the total porosity by compensated neutron logging is as follows:

wherein,to compensate for the measurements read on the neutron curve,the neutron value of the rock skeleton is shown as,is the neutron value of the fluid in the pore;

total porosity value

Value of change in secondary porosity due to fracture factors

③ rate of change of curve

Selecting curve acoustic time difference (AC) sensitive to cracks, Compensation Neutrons (CNL) and Density (DEN) to calculate curve change rate, wherein the calculation formula is as follows:

ΔX_i＝(|X_i-1-X_i|+|X_i+1-X_i|)/X_i；

wherein, X_iIs the log curve value, X, of the current depth point_i-1And X_i+1Logging curve values of two points adjacent to the current depth point;

④ rate of increase in well diameter CAL_d

The calculation formula is as follows:

CAL is the drill diameter, CAL_JThe measured hole diameter is obtained;

(3) normalization calculations were performed for each parameter:

the acoustic time difference (AC), the variation rate of a Compensation Neutron (CNL) curve, the three-porosity and the well diameter increase rate are normalized by the following formulas:

Y＝(X-X_min)/(X_max-X_min)

wherein X represents the actual measurement value of the acoustic time difference (AC), the variation rate of a Compensation Neutron (CNL) curve, the degree of three-porosity or the borehole diameter increase rate, and X_maxAcoustic time difference (AC) and complement representing the well logMaximum measurement of rate of change of Compensated Neutron (CNL) curve, rate of triple porosity or rate of increase of well diameter, X_minA sound time difference (AC) value, a Compensated Neutron (CNL) curve change rate, a minimum measurement value of a three-porosity or a borehole diameter increase rate representing the logging curve; curves F (. DELTA.AC), F (. DELTA.CNL), F (. DELTA.CAL) were obtained_d)、F(ΔΦ_P)；

The Density (DEN) rate of change is normalized using the following formula:

Y′＝1-(X′-X′_min)/(X′_max-X′_min)；

wherein X 'represents a density log measurement, X'_maxRepresenting the maximum measurement, X ', of the density log'_minA minimum measurement representing a density log; curve F (Δ DEN) is obtained;

(4) construction of fracture zone internal structure comprehensive discrimination parameter FZI

FZI＝[F(ΔAC)+F(ΔCNL)+F(ΔDEN)+F(R_TC)+F(ΔCAL_d)+F(ΔΦ_P)]/6

Wherein, F is a function relative to various curves and meets the following conditions:

wherein χ represents Δ AC, Δ CNL, Δ DEN, R_TC、ΔCAL_dOr Δ Φ_PA, b are abnormal threshold values, and a<b。