CN106089191A - 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 for Compressive Fault Zone Structure

technical field

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

Background technique

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

Compressive fracture is a reverse fault formed under the action of compressive stress field. Its force is strong, the rocks on both sides of the sliding surface are seriously broken, and the structure of the fault zone is complete, which obviously controls the accumulation of oil and gas. It is the key factor for the migration and accumulation of oil and gas in the basins of western my country. Usually, the rocks in the sliding fracture zone of the compressive fault zone are severely broken, in the form of rock powder, with fault gouge mostly developed, partly mylonitized, and the fluid passage capacity is poor, which has strong sealing ability for oil and gas (Wu Kongyou et al., 2012 ). In contrast, a large number of fractures are developed in the induced fracture zone, and the fluid passage capacity is strong, providing channels for oil and gas migration (Fu Xiaofei et al., 2005). In short, the fault zone has dual capabilities of transporting and sealing oil and gas. That is, the spatio-temporal differences in the internal structure of fault zones will lead to different roles in the process of oil and gas migration and accumulation. Therefore, predicting the structural characteristics of fault zones developed deep underground in oil and gas bearing areas is of great significance for oil and gas reservoir exploration.

For compressive faults in overlying areas, since they cannot be directly observed, how to accurately identify fault structures has always been one of the difficult problems in petroleum geological exploration. Liu Wei et al. (2013) proposed to use the four parameters of resistivity difference ratio, porosity ratio, curve change rate and diameter increase rate, combined with principal component analysis 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 lack of parameter selection and the failure to consider the range of curve changes. Zhao Yonggang et al. (2013) proposed eight parameters: three-porosity ratio, equivalent elastic modulus difference ratio, secondary porosity, dual induction amplitude difference index, cracking coefficient, relative anomaly of borehole 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 whether the fracture is developed or not is one of the important differences between the two parts of the structure. Effectively judge the internal structure of the fault zone.

Contents of the invention

The purpose of the present invention is to provide a logging identification method for compressive fault zone structure, through multi-parameter logging curve fitting, construct comprehensive discrimination parameters of fault zone structure, combined with the characteristics of the internal structure of the fault zone, quantitatively divide the compressive properties of the coverage area The internal structure of faults provides technical support for accurately evaluating the opening and closing 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 achieve:

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

(1) Determine whether the stress environment in the work area is a compressive stress environment, if it is a compressive stress environment, enter step (2);

(2) Select and calculate fracture sensitivity parameters: ① deep-shallow resistivity difference ratio R _TC , ② three-porosity logging, ③ curve change rate, ④ borehole diameter increase rate CAL _d

① Deep and shallow resistivity difference ratio R _TC :

Among them, R _D is the deep laterolog value or deep resistivity log value, R _S is the shallow laterolog value or shallow resistivity log value; the curve F(R _TC ) is obtained

② Three-porosity logging

The three-porosity logging curve includes acoustic transit time (AC), density (DEN) and compensated neutron (CNL); among them, the porosity calculated by acoustic transit time is primary porosity, and the porosity calculated by density and compensated neutron is Total porosity including at least secondary porosity of fractures and dissolution pores;

The formula for calculating primary porosity by acoustic time difference is:

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

The formula for calculating total porosity by density logging is:

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

The formula of total porosity calculated by compensated neutron logging is:

in, To compensate 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

③Curve change rate

Select curves sensitive to fractures, acoustic transit time (AC), compensated neutrons (CNL) and density (DEN) to calculate the curve change rate, and 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, and CAL _J is the measured well diameter;

(3) Perform normalized calculation for each parameter.

Curve (AC, CNL) change rate, three-porosity, diameter increase rate are normalized by the following formula:

Y＝(XX _min )/(X _max -X _min )

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

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) Construct the comprehensive discrimination 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, satisfying the following conditions:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; a</span>}\\ \mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; b</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right.$

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 well 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 structure of the fault zone), the process of identifying the internal structural logging curve of the fault zone is quantified, which is more convincing. It is of great significance to study the role of faults in controlling reservoirs. The invention checks the identification scheme by using rock core observation and imaging logging data, and finds that the division is consistent with the display of rock core and imaging logging, and verifies the accuracy of the method.

Other features and advantages of the present invention will become more apparent after 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 the quantitative identification of well logging curves for the internal structure of fractures in Well Pai 66.

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with 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, and if it is a compressive stress environment, proceed to 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.

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

① Deep and shallow resistivity difference ratio R _TC :

Among them, _{RD is the deep laterolog value or deep resistivity log value, R S is} the shallow laterolog value or shallow resistivity log value; the curve F(R _TC ) is obtained;

② Three-porosity logging

The three-porosity logging curve includes acoustic transit time (AC), density (DEN) and compensated neutron (CNL); among them, the porosity calculated by acoustic transit time is primary porosity, and the porosity calculated by density and compensated neutron is Total porosity including at least secondary porosity of fractures and dissolution pores;

The formula for calculating primary porosity by acoustic time difference is:

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

The formula for calculating total porosity by density logging is:

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

The formula of total porosity calculated by compensated neutron logging is:

in, To compensate 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

③Curve change rate

Select curves sensitive to fractures, acoustic transit time (AC), compensated neutrons (CNL) and density (DEN) to calculate the curve change rate, and 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, and CAL _J is the measured well diameter;

(3) Perform normalized calculation for each parameter.

Curve (AC, CNL) change rate, three-porosity, diameter increase rate are normalized by the following formula:

Y＝(XX _min )/(X _max -X _min )

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

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) Construct the comprehensive discrimination 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, satisfying the following conditions:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; a</span>}\\ \mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; b</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right.$

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 northwestern margin of the Junggar Basin. The Junggar Basin is an important oil-gas-bearing basin in western my country. It experienced tectonic movements from the Hercynian to the Himalayas, and developed compressive faults. The faults have been active for a long time, have a long horizontal extension distance, and 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: hanging wall induced fracture zone, sliding fracture zone and footwall induced fracture zone. Compared with the induced fracture zones of the two plates, the R _TC value of the sliding fracture zone is negative or zero, indicating that fractures are not developed; the CAL _d value is obviously smaller and relatively stable, implying that the 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 have small changes, but the induced fracture zones have obvious jumps; Φ _P is stable, which is related to the overall lithology being mudstone; FZI is It presents an obviously low value, indicating that fractures are not developed in the sliding fracture zone as a whole, but 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, rather than 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 Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; 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 various embodiments of the present invention.

Claims (1)

1. A well logging identification method for compressive fault zone structure, is characterized in that, comprises the steps: (1) Determine whether the stress environment in the work area is a compressive stress environment, if it is a compressive stress environment, enter step (2); (2) Select and calculate fracture sensitivity parameters: ① deep-shallow resistivity difference ratio R _TC , ② three-porosity logging, ③ curve change rate, ④ hole diameter increase rate CAL _d ; ① Deep and shallow resistivity difference ratio R _TC : Among them, _{RD is the deep laterolog value or deep resistivity log value, R S is} the shallow laterolog value or shallow resistivity log value; the curve F(R _TC ) is obtained; ② Three-porosity logging The three-porosity logging curve includes acoustic transit time (AC), density (DEN) and compensated neutron (CNL); among them, the porosity calculated by acoustic transit time is primary porosity, and the porosity calculated by density and compensated neutron is Total porosity including at least secondary porosity of fractures and dissolution pores; The formula for calculating primary porosity by acoustic time difference is: Among them, Δt is the formation acoustic time difference read from the acoustic time difference curve, Δt _f is the acoustic time difference of the fluid in the pores, and Δt _ma is the acoustic time difference of the rock skeleton; The formula for calculating total porosity by density logging is: Among them, ρ _b is the measured value read out from the density logging curve, ρ _f is the density value of the fluid in the pores, and ρ _ma is the density value of the rock skeleton; The formula of total porosity calculated by compensated neutron logging is: in, To compensate 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 ③Curve change rate Select curves sensitive to fractures, acoustic transit time (AC), compensated neutrons (CNL) and density (DEN) to calculate the curve change rate, and 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, and CAL _J is the measured well diameter; (3) Perform normalized calculations for each parameter: Curve (AC, CNL) change rate, three-porosity, diameter increase rate are normalized by the following formula: Y＝(XX _min )/(X _max -X _min ) Among them, X represents the actual measured value of the change rate of the curve (AC, CNL), three-porosity or borehole diameter increase rate, and X _max represents the change rate of the curve (AC, CNL) of the log curve, three-porosity or borehole diameter The maximum measured value of the increase rate, X _min represents the change rate of the curve (AC, CNL) of this type of logging curve, the minimum measured value of the three-porosity or the diameter increase rate; the curves F(ΔAC), F(ΔCNL), F(ΔCNL), F(ΔCAL _d ), F(ΔΦ _P ); 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) Construct the comprehensive discrimination 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, satisfying the following conditions: $\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; a</span>}\\ \mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; b</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right.$ 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.