CN111077592A

CN111077592A - Evaluation method of fault lateral plugging master control factors

Info

Publication number: CN111077592A
Application number: CN201911338406.XA
Authority: CN
Inventors: 蒋有录; 王宇; 苏圣民; 赵凯
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2019-12-23
Filing date: 2019-12-23
Publication date: 2020-04-28
Anticipated expiration: 2039-12-23
Also published as: CN111077592B

Abstract

The invention provides an evaluation method of fault lateral plugging main control factors, and belongs to the technical field of oil and gas exploration. The method improves the existing lithological opposition calculation method, combines the lithological smearing result, comprehensively evaluates the main control factors of the lateral fault plugging of the study area, can provide reference for next drilling control and distribution, and effectively reduces the exploration risk. The technical scheme comprises the steps of calculating the ratio V1% of fault lithologic opposite plugging, the ratio V2% of fault plastic coated plugging and the ratio V3% of other factors, and judging main control factors of fault lateral plugging. The invention can be applied to oil-gas geological exploration.

Description

Evaluation method of fault lateral plugging master control factors

Technical Field

The invention belongs to the technical field of oil-gas exploration, and particularly relates to an evaluation method for fault lateral plugging main control factors.

Background

The fault is a structure formed by that the earth crust is broken by stress, and rock blocks on two sides are obviously and relatively displaced along the broken surface. In a continental facies fault basin, a fault is a key channel for communicating a hydrocarbon source rock and a reservoir stratum and is a key position of a reservoir, and whether the fault can be laterally blocked or not is of great significance to fault type oil and gas reservoirs.

The control factors of fault lateral plugging are lithologic opposite plugging, plastic smearing, fracture action sealing and the like. Wherein, the qualitative and quantitative research can be carried out by plastic smearing and lithologic opposite plugging. For lithologic opposite plugging, a Knipe graph method and an Allan graph method are available at present, wherein the Knipe graph method is that the lithologic properties of the stratum in the extension direction of the fracture surface are assumed to be consistent, and then quantitative depiction is carried out by taking the fracture distance as a variable; the Allan method is characterized by sequentially explaining seismic sections along the fault direction and has limitations.

For plastic coating plugging, SGR is a common parameter for quantitatively researching plastic coating, is widely applied to various large oil fields, and generally has the meaning that a fault below a critical value cannot plug oil gas, the fault above the critical value can effectively plug oil gas, and the determination of the critical value is generally the lowest value of a test oil gas zone section. However, the research shows that the part (without plastic coating) with the SGR of 0 can also block oil gas due to other factors, which indicates that the lateral blocking performance of the fault cannot be comprehensively analyzed only by researching the SGR, and the selection of the lower limit value is not completely practical.

At present, geologists often start from a fault lateral blocking factor and analyze the fault lateral blocking performance by using different technologies, but cannot comprehensively characterize the influence factors of the fault lateral blocking from a single factor, and further cannot quantitatively research the main control factors of the fault lateral blocking.

Disclosure of Invention

The invention provides an evaluation method of fault lateral plugging main control factors, which is used for judging the main control factors of fault lateral plugging based on the plastic smearing degree and lithological opposition relation of an oil-gas layer section, providing reference for next drilling control and distribution and effectively reducing exploration risks.

In order to achieve the purpose, the invention provides an evaluation method of fault lateral blocking main control factors, which comprises the following steps:

1. calculating the ratio V1% of the fault lateral plugging factor to the interruption of lithologic opposite plugging:

resampling lithology data of wells on the upper and lower sides of an original oil and gas well fault, and dividing the lithology data into lithology sequences (a is 0.1) according to a depth sampling rate of a m, wherein a value of a sandstone sequence is 1, and a value of a mudstone sequence is 0; according to the inclination relation of the stratum and the fault, a projection formula is selected to project the resampled lithology sequence to the fault plane to form a corresponding 'fracture well' in a virtual mode, namely the lithology data of the well is reasonably stretched according to the proportion to construct the well with the fracture surface, and the method comprises the following specific steps:

according to the dip relation of the stratum and the fault, selecting different projection formulas to project the new lithology sequence to the fault plane, which specifically comprises the following steps:

when the trend of the fault is opposite to that of the stratum, the conversion relation between the fracture well and the original oil and gas well is as follows:

when the trend of the fault is the same as that of the stratum, the conversion relation between the fracture well and the original oil and gas well is as follows:

wherein Xn is a fracture well, X is an original drilled well, the molecular formula on the right side of X is a tensile coefficient, α 1 is a stratum inclination angle when the inclination of a fault is opposite to that of a stratum, α 2 is a stratum inclination angle when the inclination of the fault is the same as that of the stratum, and β is a fault inclination angle.

In conjunction with fig. 3(a), the formula is derived as follows:

when the tendency of a fault is opposite to that of a stratum, the drilling well is made to meet two points of a certain stratum A, B, the thickness is X1, ∠ ABC is 90- α 1, the true thickness AC of the stratum is X1 sin (90- α 1), and the corresponding point of the section in the profile well is HI AD AC/sin (α 1+ α 0), X1 sin (90- α 1)/sin (α 1+ β), X1 cos (α 1)/sin (α 1+ β);

when the tendency of a fault and a stratum is the same, a drilling drill meets two points of a certain stratum F, H and has the thickness of X2, firstly, it can be seen that ∠ HEG is β - β 02, FH is 90 degrees with the horizontal line, ∠ EHF is 90 degrees- β 1 degrees, in a right triangle delta EHG, ∠ FHG is 180 degrees- ∠ EGH- ∠ HEG- ∠ EHF is 180 degrees-90 degrees- (β 5- β 22) - (90 degrees- β) is β 32, the true thickness GH of the stratum is obtained and is X2 cos (β 42), and the stratum in a fracture well corresponds to KM EH is X2 cos (β 62)/sin (β - α 2).

The derivation is a calculation method of a certain stratum, when actual calculation is performed, all lithological data of all the strata in a drilled well need to be converted into a fault plane, it can be seen from fig. 3(b) that each stratum in a fracture well is stretched, when a stratum inclination angle and a fault inclination angle corresponding to the section of stratum change at different depths, it is necessary to count each stratum and the corresponding fault inclination angle, that is, the stretching degree changes correspondingly according to the stratum inclination angle and the fault inclination angle.

And summing the lithological sequence values of the profile wells generated at two sides of the fault at the same depth to obtain the lithological opposite relation. For example, if the cumulative value of the calculated point depth lithology is 1, then the lithology opposition of mudstone-sandstone; if the accumulated value is 2, the sandstone-sandstone opposite relation is obtained; if the accumulated value is 0, the opposite relation of mudstone and mudstone is obtained. Counting the number S1 of the sum of lithological sequence values in the oil interval being 1 and the number N of the oil and gas intervals, and dividing S1 by N to obtain the ratio V1% of lithological opposite plugging;

2. calculating the ratio V2% of the plastic coating plugging of the fault side plugging factor:

calculating fault distance D according to the earthquake section with the shortest distance between the cut oil-gas well and the section, calculating the sum sigma Hi of the thicknesses of all mudstone layers in the target interval according to lithological data, and calculating by using a fault smearing parameter formula SGR which is sigma Hi/D to obtain the SGR value of the top point of the oil-gas interval in the target interval; then counting the number S2 of lithological sequences in the oil-gas interval in the target interval, wherein the lithological sequences are not 1, and the SGR value in the oil-gas interval is not 0, and the number N of the oil-gas interval in the target interval, and dividing S2 by N to obtain the ratio V2% of the plastic coating plugging;

3. calculating the ratio V3% of other factors in fault lateral blocking factors:

V3％＝(N-S1-S2)/N；

4. judging main control factors of fault lateral plugging:

the maximum value of V1%, V2% and V3% is selected as a main control factor for lateral fault plugging.

Compared with the prior art, the invention has the advantages and positive effects that:

when the lithological opposition relationship of the two sides of the fault is calculated, besides the fault dip angle, the method also fully considers the stratigraphic dip angles of the upper fault tray and the lower fault tray, based on the well lithological data of the two sides of the fault, the lithological opposition relationship between the upper fault tray and the lower fault tray is visually and quantitatively represented by projecting to the section, and the result of the lithological opposition relationship has higher longitudinal precision and better accords with geological reality.

Drawings

FIG. 1 is a flow chart of a method for quantitatively analyzing lateral blocking factor of a fault according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a reclaimed northeast 403 well-reclaimed northeast 13 well through the well provided by the embodiment of the present invention;

fig. 3(a) is a schematic diagram of a fracture well construction under the same single fault and single stratum dip relationship and different conditions provided by the embodiment of the invention, and (b) is a schematic diagram of a multi-stratum fracture well construction.

Detailed Description

In order to describe the evaluation method of the fault lateral blocking main control factor provided by the embodiment of the invention in more detail, the technical solution in the embodiment of the invention will be described clearly and completely below, and it is obvious that the described embodiment is only a part of the embodiment of the invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Taking the reclamation of northeast China as an example, the reclamation of the northeast China near yellow river mouth depression, the western inoculation of the dip forest-enriching depression and the long dike-soliton bulge, the southern adjacent Qingdong depression and the Qing lump bulge, the east inoculation of the northeast China low bulge and the Laizhou bay depression have the exploration area of about 396km². The type of the oil and gas reservoir is mainly a fault type oil and gas reservoir, and the fault is used as an important boundary for laterally blocking oil and gas and needs to be studied finely. Factors affecting lateral blocking of faults can be summarized as lithological opposition, plastic smearing and other factors. The following three factors are surrounded, the main control factors of fault lateral plugging in the reclamation northeast region are analyzed, and the specific working flow is shown in figure 1。

1. Calculating the ratio V1% of the lithologic opposite blocking of the fault layer;

the oil gas is enriched in different depth sections, taking fault lower disk reclamation northeast 403 wells as an example, actual oil production is totally twelve small layers (see table 5), and four layers of oil layer lithological data are taken as an example (table 1) for saving space due to calculation related to the following tables 3 and 4.

TABLE 1 original lithology data (part) for reclaiming northeast 403 well

Top depth (m)	Bottom depth (m)	Lithology
			1171	1174	Yellow oil-immersed sandstone
1231	1235	Fine sand stone with gray oil stain
			1416.5	1419	Gray fluorescent sandstone containing gravel
1616	1617	Grey tuff sandstone

In this embodiment, the lithology data is resampled at intervals of 0.1m, the lithology number sequence is converted into a number, the sandstone is converted into 1, and the mudstone is converted into 0.

As shown in fig. 2, after cutting the seismic section of the reclaimed northeast 403 and the fault, selecting C, D two points on the section to calculate the fault dip angle; two points A, B of the formation are selected to calculate the dip angle of the dip pan. The vertical distance and the horizontal distance of the two points are counted, the respective inclination angles can be calculated by utilizing the arctan trigonometric function, and the calculation results are shown in the table 2.

TABLE 2 determination of fault dip and formation dip

The lithology data of the oil and gas well is converted to the fracture surface by using the projection formula 1 or 2 according to the relation between the fault and the stratum inclination angle, and the relative 'fracture surface well' is assumed as shown in figure 3 (a). In FIG. 3(a), X1 and X2 are hydrocarbon wells, X1 new and X2 new are profile wells.

Specifically, the trend of the fault and the stratum of the northeast 403 well to be reclaimed is the same, the fault dip angle and the stratum dip angle are substituted into the formula 2, and the step of projecting the original well data to the fracture surface to form the fracture surface well is completed, and the result is shown in table 3.

TABLE 3 reclaiming northeast 403 fracture well petrophysical sequence (part)

Similarly, the reclaimed northeast 13 wells on the other plate of the fault are converted in the same way to obtain the lithology sequence of the fracture well corresponding to the upper plate of the fault, specifically, the faults and the stratums of the reclaimed northeast 13 wells have the same tendency, the fault dip angle and the stratum dip angle are substituted into the formula 2 to complete the step of projecting the original well data to the fracture surface to form the fracture surface well, the lithology sequence of the well and the reclaimed northeast 403 wells are simultaneously placed under the fracture surface coordinate system for comparison, the lithology sequences of the well and the reclaimed northeast 403 wells are accumulated, and the result is shown in table 4.

TABLE 4 cumulative results (part) of lithology series of upper and lower walls of fault

And by analogy, calculating all oil and gas well sections. As shown in table 5, the number of hydrocarbon intervals of the 403 well in northeast of reclamation was 12, the point with the lithology sequence sum of 1 was counted as sand-mud, and S1 ═ 10 and V1 ═ S1/N ═ 10/12 ═ 83.33% were calculated.

2. Calculating the ratio V2% of the plastic smearing and blocking of the fault;

and (4) counting the SGR value of the top of the oil and gas interval by using the resampled lithological sequence and using a formula SGR ═ Sigma Hi/D. As shown in table 5, in the hydrocarbon interval, the number S2 was counted, in which the sequence of lithologies was not 1 (non-lithology opposite), and the SGR value in the hydrocarbon interval was not 0 (lithology smear was present). Dividing S2 by N, the ratio of blocking by plastic application, V2% ═ S2/N ═ 1/12 ═ 8.33%, was obtained.

TABLE 5 comprehensive calculation results of the sealing performance of oil-producing zone of 403 well reclaimed in northeast

As can be seen from table 5, the SGR corresponding to the original depth 1171m is 0, which means that there is no mudstone smearing, but there is lithologic opposition, and belongs to the category of V1 calculation; mud rock smearing exists in 1231m, but SGR is low, which represents weaker mud rock smearing and has lithological opposition; 1416.5m represents that relatively good mudstone smearing and lithology opposition exist, the sum of the two layers of lithology sequences is 1, and the two layers of lithology sequences belong to the calculation category of V1; 1616m represents only mudstone smear, no lithological opposition, which belongs to the category of V2 calculations. 1466.5m has neither lithologic opposite smearing nor mudstone smearing, and therefore, neither is in the category of V1 and V2, and belongs to the category of V3 calculation.

V3％＝(12-10-1)/12＝1/12＝8.33％。

4. judging main control factors of fault lateral plugging:

in the fault lateral plugging factors, the ratio V1% of lithologic opposite plugging of a fault is 83.3%, the ratio V2% of plastic coated plugging of the fault is 8.3%, and the ratio V3% of other factors is 8.4%, so that V1% is greater than V2% and is V3%, and V1% is the maximum value, and the lithologic opposite plugging is judged to be the main factor of the fault plugging of the region. After the main control factor of the lateral blocking of the fault in the region is determined to be lithological opposite, the next step of drilling is to preferentially consider the region with good lithological opposite, and less consider the region controlled by mudstone smearing and other factors.

Claims

1. The evaluation method of the fault lateral blocking main control factor is characterized by comprising the following steps:

(1) calculating the ratio V1% of the fault lateral plugging factor to the interruption of lithologic opposite plugging:

resampling lithology data of wells on the upper and lower sides of an original oil and gas well fault, and dividing the lithology data into lithology sequences according to a depth sampling rate of 0.1m, wherein the value of a sandstone sequence is 1, and the value of a mudstone sequence is 0; according to the dip relation of the stratum and the fault, selecting a projection formula to project the lithology sequence to the fault plane to form a corresponding virtual well, specifically:

when the trend of the fault is opposite to that of the stratum, the conversion relation between the fracture well and the original well is as follows:

when the trend of the fault is the same as that of the stratum, the conversion relation between the fracture well and the original well is as follows:

wherein Xn is a fracture well, X is an original drilling well, the molecular formula on the right side of X is a tensile coefficient, α 1 is a stratum inclination angle when the inclination of a fault is opposite to that of a stratum, α 2 is a stratum inclination angle when the inclination of the fault is the same as that of the stratum, and β is a fault inclination angle;

accumulating the lithological sequence values of all depths of the fracture well, counting the number S1 of upper and lower tray lithological sequence values of 1 of an oil interval in the target interval and the number N of the oil-gas interval in the target interval, and dividing N by S1 to obtain the lithological opposite plugging rate V1%;

(2) calculating the ratio V2% of the plastic coating plugging of the fault side plugging factor:

under a vertical depth coordinate system, the thickness sum of all shale layers Hi in a target interval is calculated according to lithological data, the fault distance D is calculated according to a seismic section with the shortest distance between a cut oil-gas well and the fault, and the SGR value of the top point of the oil-gas interval in the target interval is calculated by utilizing a fault smearing parameter formula; then counting the number S2 of lithological sequences in the oil-gas interval in the target interval, wherein the lithological sequences are not 1, and the SGR value in the oil-gas interval is not 0, and the number N of the oil-gas interval in the target interval, and dividing S2 by N to obtain the ratio V2% of the plastic coating plugging;

(3) calculating the ratio V3% of other factors in fault lateral blocking factors:

V3％＝100％-V1％-V2％；

(4) judging main control factors of fault lateral plugging:

and judging that the maximum value of V1%, V2% and V3% is a main control factor for lateral fault plugging.