Sand body model description method for sandstone-mudstone interbedded reservoir

Abstract

The invention discloses a sand body model description method for a sand-mudstone interbed reservoir, comprising: drawing an identification standard line in a scatter plot to identify a possible development area of ​​a columnar sand body; establishing a well-layer coordinate system in the possible development area of ​​the columnar sand body; describing an inherited channel core and a growth channel wing in an envelope manner on the well-layer coordinate system and a reservoir profile diagram that overlap each other; splicing envelope graphics that respectively represent the inherited channel core and the growth channel wing to obtain a spliced ​​graphic; the spliced ​​graphic is used to describe a spanning cut body, and the spanning cut body is the sand body model of the sand-mudstone interbed reservoir; and the problem that the existing conventional research methods cannot provide a sand body geological model for a river-delta sand-mudstone interbed reservoir is solved.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum development, and in particular to a sand body model description method of a river-delta sandstone-mudstone interlayer reservoir. Background Art

[0002] The Daqing Changyuan is mainly composed of river-delta deposits, with relatively developed river channels with good physical properties and dominant reservoirs. Vertical superposition of sand bodies is often observed on the profile. The essence of this sand body superposition is the erosion and cutting of the previous river channel by the later river channel, which then forms a thicker columnar sand body that exceeds the thickness of a single development layer.

[0003] In the area where the sand bodies do not overlap vertically, obvious, stable and continuous mudstone interlayers will develop between the development layers. These mudstone interlayers have relatively no permeability and isolate the fluids in the adjacent development layers.

[0004] However, these columnar sand bodies have good vertical permeability due to the lack of mudstone interlayers. During the displacement process, the injected fluid inside the columnar sand body will deviate from the originally horizontal design direction under the influence of gravity and flow downward into the underlying strata. The strata originally designed for development cannot be effectively displaced due to this layer interference, forming a weak development zone with rich residual oil.

[0005] Although existing research methods have good results in sedimentary phase identification, program stratigraphic division, sand body feature description, etc., most of them are limited to the fine dissection of sand bodies within the development layer and well network, ignoring the interference phenomenon of layer channeling in the actual development process. The actual situation is: the description of sand bodies in conventional reservoirs is based on sedimentary phases, which makes it difficult to show the structural characteristics of composite sand bodies with multiple sedimentary phases; the description of well relationships is based on well networks, which makes it difficult to directly solve the interference characteristics of multiple well networks; the analysis of injection and production characteristics is based on layer segments as vertical production units, which makes it difficult to evaluate layer channeling interference and other conditions.

[0006] Therefore, the existing technology has failed to establish a geological model for the cross-section columnar sand bodies of the river-delta sandstone-mudstone interbedded reservoir that crosses the sedimentary phase boundaries geologically, the well network boundaries engineeringly, and the layer boundaries in scale. It is unable to quickly identify the columnar sand bodies, describe the vertical connection areas of the reservoirs, and determine the interference of the interlayers. It lacks the necessary technical means to ultimately characterize the remaining oil-enriched weak production areas. Summary of the invention

[0007] The present invention discloses a sand body model description method for a river-delta sandstone-mudstone interbed reservoir, which solves the problem that existing conventional research methods cannot provide a sand body geological model for a river-delta sandstone-mudstone interbed reservoir.

[0008] To achieve the above-mentioned object of the invention, the sand body model description method of the sand-mudstone interbedded reservoir is characterized by comprising:

[0009] Draw identification standard lines in the scatter plot to identify possible development areas of columnar sand bodies;

[0010] Establishing a well-layer coordinate system in the area where the columnar sand body may develop;

[0011] Describing the inherited channel core and the growing channel wing in an envelope manner on the well-layer coordinate system and the reservoir cross-section diagram that are superimposed on each other;

[0012] The inherited channel core is a columnar sand body in the reservoir that continuously spans two or more development layers and has no mudstone interlayer blocking the vertical seepage; the growth channel wing is a sand body directly connected to the inherited channel core in the horizontal direction;

[0013] splicing the envelope graphs representing the inherited channel core and the growing channel wing respectively to obtain a spliced ​​graph;

[0014] The splicing graph is used to depict the cross-cutting stack, and the cross-cutting stack is used as the sand body model of the sandstone-mudstone interbedded reservoir.

[0015] Preferably, the scatter plot is drawn with sandstone thickness as the horizontal coordinate and effective thickness as the vertical coordinate.

[0016] Preferably, the method for drawing the identification standard line includes:

[0017] Performing linear regression fitting on all scattered points in the scatter plot to obtain a first identification standard line;

[0018] The second identification standard line is obtained by taking the ratio of the average effective thickness to the average sandstone thickness as the slope.

[0019] Preferably, the area above the identification standard line is the possible development area of ​​the columnar sand body.

[0020] Preferably, the method for establishing the well-layer coordinate system comprises:

[0021] Select several wells in the area where the columnar sand bodies may develop;

[0022] The well point position of the well is taken as the horizontal axis coordinate point of the coordinate system, and the top interface of the stratum vertically crossed by the well is taken as the vertical axis coordinate point of the coordinate system.

[0023] Preferably, the method of superimposing the well-layer coordinate system and the reservoir profile diagram comprises:

[0024] Drawing a reservoir cross-section map in the well-layer coordinate system according to the reservoir interpretation results;

[0025] During the drawing process, the well-layer coordinate system is made to completely correspond to the wells and strata in the reservoir cross-section diagram to complete the mutual superposition.

[0026] Preferably, the method of characterizing the inherited channel core and the growing channel wing in an envelope manner includes:

[0027] On the superimposed well-layer coordinate system and reservoir profile, all inherited channel cores and growth channel wings are marked;

[0028] The calibrated inherited channel core and the growth channel wing are enclosed to characterize the inherited channel core and the growth channel wing.

[0029] Preferably, the enveloping method comprises:

[0030] Enveloping the inherited channel core and the growing channel wing by a rectangular outline;

[0031] During the enveloping process, the four sides of the rectangle intersect with the sand body respectively, and the sand body is inside the rectangle.

[0032] The present invention has the following beneficial effects:

[0033] The method of the present invention first gives the definitions of inherited channel cores, growing channel wings and spanning incision bodies, and then based on the identification standard line, identifies the position where the inherited channel core may develop through the standard line, realizes the rapid identification of columnar sand bodies, and solves the problem that the vertically connected areas in the river-delta reservoir are difficult to identify; and then continues to establish a well-layer coordinate system to envelop and characterize the inherited channel cores and growing channel wings, further characterize and describe the spanning incision bodies, and establish a geological model of spanning incision bodies with core-wing characteristics that crosses the sedimentary phase boundary in geology, crosses the well network boundary in engineering, and crosses the layer boundary in scale, thereby solving the problem that there is no specific sand body geological model for the river-delta sandstone and mudstone interlayer reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings herein are incorporated into the specification and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and are used to illustrate the technical solutions of the present disclosure together with the specification.

[0035] Figure 1 is a flow chart of a sand body model description method for a sand-mudstone interbedded reservoir according to the disclosed method;

[0036] Figure 2 It is a schematic diagram of the geological model of the inherited channel core and the growing channel wing of the disclosed method;

[0037] Figure 3 is a schematic diagram of a geological model spanning a cut stack according to the disclosed method;

[0038] Figure 4 It is a schematic diagram of the identification standard line;

[0039] Figure 5 is a schematic diagram of the well-layer coordinate system of the disclosed method;

[0040] Figure 6 It is the identification standard line of the B12W block in the embodiment of the present disclosure;

[0041] Figure 7 It is a schematic diagram of the well-layer coordinate system of the B12W block in the embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] The present invention is described below based on embodiment, but it is worth noting that the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. However, for the part not described in detail, those skilled in the art can also fully understand the present invention.

[0043] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0044] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0045] Since the cross-section of the river-delta sandstone-mudstone interbedded reservoir has vertically superimposed sand bodies and columnar sand bodies that exceed the thickness of a single development layer, it is composed of a combination of sand bodies of various sedimentary phases. In terms of morphology, it can be within one well network or across multiple well networks, and it will occupy at least two development layers in terms of location.

[0046] Therefore, when such columnar sand bodies develop in the reservoir, it is necessary to establish a geological model that spans different sedimentary phases, different well networks, and different strata, and then identify the columnar sand bodies, describe the vertical connectivity areas of the reservoir, determine the interference of the interlayers, and finally characterize the residual oil-rich weak development areas of the reservoir.

[0047] Therefore, for the river-delta sandstone-mudstone interbed reservoir, in order to accurately locate the weak production area, the embodiment of the present disclosure provides the definitions of the inherited channel core, the growth channel wing and the spanning incision body, specifically:

[0048] The definition of the inherited channel core is: a columnar sand body in the reservoir that continuously spans two or more development layers and has no vertical seepage blocked by mudstone interlayers. Its formation is controlled by the mutual inheritance between channels of different periods and the retention sedimentation within the channel ( Figure 2 ).

[0049] The definition of the growth channel wing is: the sand body directly connected to the inherited channel core in the horizontal direction. Its formation is mainly controlled by the circulation accumulation inside the channel, and mudstone interlayers are developed between the sand bodies in the vertical direction ( Figure 2 ).

[0050] The definition of the cross-cutting body is: a sand body formed by the inherited channel core and the growth channel wing ( Figure 3 ).

[0051] From the above definition, it can be seen that the straddling incision body covers all sedimentary phase types corresponding to river channel deposits and the sand bodies connected thereto, and crosses the sedimentary phase boundary geologically; it can develop between injection and production wells and span multiple well networks, and crosses the well network boundary in engineering; there are no mudstone interlayers developed inside, and there are no separation boundaries between development layers. It has good vertical seepage capacity and crosses the layer boundary in scale.

[0052] That is, in order to adapt to the characteristics of river-delta sandstone-mudstone interbedded reservoirs, the disclosed method needs to establish a cross-cutting geological model with core-wing characteristics that crosses the sedimentary phase boundary geologically, crosses the well network boundary in engineering, and crosses the layer boundary in scale.

[0053] In order to achieve the above-mentioned object of the invention, the present invention provides the following specific technical solutions:

[0054] Figure 1 is a flow chart of a sand body model description method for a sand-mudstone interbedded reservoir according to an embodiment of the present invention; Figure 1 The sand body model description method of the interbedded sandstone and mudstone reservoir comprises: step S1: drawing an identification standard line in a scatter plot to identify the possible development area of ​​columnar sand bodies; step S2: establishing a well-layer coordinate system in the possible development area of ​​the columnar sand bodies, and depicting the inherited channel core and the growth channel wing in an envelope manner on the superimposed well-layer coordinate system and the reservoir profile; step S3: splicing the envelope figures representing the inherited channel core and the growth channel wing respectively to obtain a spliced ​​figure, the spliced ​​figure is used to depict the cross-cutting body, and the cross-cutting body is used as the sand body model of the interbedded sandstone and mudstone reservoir.

[0055] Specifically, the technical solution will be described in detail below in conjunction with specific embodiments and drawings. Example

[0056] The disclosed method is specifically applied to the B12W block in Changyuan, Daqing. The detailed steps are as follows:

[0057] Step S1: Draw an identification standard line in the scatter plot to identify the possible development area of ​​columnar sand bodies.

[0058] 1. Draw the identification standard line

[0059] (1) Data preparation

[0060] By using existing technical means, single well core description, logging interpretation, seismic inversion and other reservoir analysis work was carried out in the B12W block to identify the lithological characteristics of the single well in the target development layer, divide the three main lithological types of mudstone, sandstone and effective sandstone, and measure and count the thickness of different lithologies.

[0061] (2) Draw a scatter plot

[0062] Using all the single well data, a scatter plot of effective thickness and sandstone thickness was drawn with sandstone thickness as the horizontal axis and effective thickness as the vertical axis.

[0063] (3) Draw the identification standard line

[0064] Collect the sandstone thickness and effective thickness values ​​of all wells in the target development layer, and divide the cumulative total thickness by the total number of wells to calculate the average effective thickness S of all wells in the study area. y (m), average sandstone thickness S s (m).

[0065] With sandstone thickness as the x-axis and effective thickness as the y-axis, a scatter plot of the ratio of effective thickness to sandstone thickness at each well point in the study area was drawn, and linear regression fitting was performed on all the scatter points to obtain the first identification standard line: y1=ax+b.

[0066] Based on the average effective thickness and the average sandstone thickness, the slope k (k=S y / S s ), and then get the second identification standard line y2=kx.

[0067] 2. Identify possible development areas of columnar sand bodies

[0068] The channel core is the area where sandstone is concentrated. The higher the degree of sandstone development, the greater the possibility of channel core development. The identification standard line reflects the average degree of sandstone development in the whole area. Above the standard line, the degree of sandstone development is better than the average characteristics of the whole area. The higher the sandstone development, the more likely it is to develop a channel core ( Figure 4 ).

[0069] Figure 6 is the B12W block identification standard line of the embodiment of the present disclosure; Figure 6The well locations corresponding to the scattered points above the two identification standard lines are the locations where inherited channel cores may develop. The farther the scattered points are from the two identification standard lines, the greater the possibility of developing inherited channel cores.

[0070] Step S2: establishing a well-layer coordinate system in the area where the columnar sand body may develop; and depicting the inherited channel core and the growth channel wing in an envelope manner on the superimposed well-layer coordinate system and the reservoir profile.

[0071] 1. Establish well-layer coordinate system

[0072] The establishment method is: select a number of wells, take the well positions of these wells as the horizontal axis coordinate points of the coordinate system, take the top interface of the stratum vertically crossed by these wells as the vertical axis coordinate points of the coordinate system, and the unit length of the vertical axis represents the thickness of the corresponding stratum, and establish the well-layer coordinate system ( Figure 5 ).

[0073] In the well-layer coordinate system, the horizontal axis is the multiple of the well spacing, and the vertical axis is the minimum number of development layers.

[0074] Figure 7 is a schematic diagram of the well-layer coordinate system of the B12W block of the present disclosure embodiment; Figure 7 middle:

[0075] (1) Main well locations of the profile: Based on the possible development area of ​​columnar sand bodies identified in step S1, four wells O1, W2, O2, and W3 were selected from the northwest to southeast direction;

[0076] (2) Improve the well locations of the profile: select well W1, which is the nearest neighbor to the northwest of well O1, and well O3, which is the nearest neighbor to the southeast of well W3, for expansion. The six wells that ultimately constitute the profile are wells W1, O1, W2, O2, W3, and O3.

[0077] (3) Determine the vertical axis: Take the well W1 on the most northwest side as the vertical axis, and the unit of the vertical axis is the layer interval;

[0078] (4) Determine the horizontal axis: The bottom interface of the development layer is used as the vertical and horizontal axes. The horizontal axis unit is a single well, and the unit length is the well spacing.

[0079] 2. The method of describing the inherited channel core and the growth channel wing in an envelope manner on the superimposed well-layer coordinate system and reservoir profile is:

[0080] (1) Superimposed well-layer coordinate system and reservoir profile

[0081] Draw a reservoir profile in the well-layer coordinate system according to the reservoir interpretation results. During the drawing process, the size of the existing reservoir profile between the corresponding wells can be enlarged or reduced in non-uniform proportion according to the horizontal and vertical proportions of the coordinate system, so that the well-layer coordinate system and the wells and strata in the reservoir profile are completely corresponding and the two are superimposed on each other.

[0082] (2) Demarcating the inherited channel core and the growing channel wing

[0083] On the superimposed well-layer coordinate system and reservoir profile, all columnar sand bodies spanning double the vertical unit length are found. The locations of these columnar sand bodies are the development locations of inherited channel cores. Secondly, the sand bodies connected to the inherited channel cores in the horizontal direction are found. These sand bodies are the growth-type channel wings. Finally, all inherited channel cores and growth-type channel wings are calibrated.

[0084] (3) Enveloping and characterizing the inherited channel core and the growing channel wing

[0085] The columnar sand body (inherited channel core) that spans twice the vertical unit length is enclosed by a rectangular outline. During the enveloping process, the four sides of the rectangle intersect with the sand body respectively, while ensuring that the sand body is completely inside the rectangle, so as to achieve the purpose of characterizing and describing the development position and basic morphology of the inherited channel core in the well-layer coordinate system.

[0086] The same rectangular contour enveloping method is used to envelop the calibrated and identified growth-type channel wing, so as to achieve the purpose of characterizing and describing the development position and basic morphology of the growth-type channel wing in the well-layer coordinate system.

[0087] Step S3: splicing the envelope figures representing the inherited channel core and the growth channel wing respectively to obtain a spliced ​​figure, wherein the spliced ​​figure is used to depict the cross-cutting body; the cross-cutting body is the sand body model of the sandstone-mudstone interbedded reservoir.

[0088] The rectangles representing the inherited channel core and the growth channel wing in step S2 are stitched together to form a polygon. This polygon is used to characterize and describe the developmental position and basic morphology of the cross-cutting body in the well-layer coordinate system.

[0089] The cross-cutting body is the sand body model of the sandstone-mudstone interbedded reservoir.

[0090] The above-mentioned embodiments are only embodiments of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, without departing from the concept of the present invention, several variations, equivalent substitutions, improvements, etc. can be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A sand body model description method for a sand-mudstone interbedded reservoir, characterized in that: include: Draw identification standard lines in the scatter plot to identify possible development areas of columnar sand bodies; Establishing a well-layer coordinate system in the area where the columnar sand body may develop; Describing the inherited channel core and the growing channel wing in an envelope manner on the well-layer coordinate system and the reservoir cross-section diagram that are superimposed on each other; The inherited channel core is a columnar sand body in the reservoir that continuously spans two or more development layers and has no mudstone interlayer blocking the vertical seepage; the growth channel wing is a sand body directly connected to the inherited channel core in the horizontal direction; splicing the envelope graphs representing the inherited channel core and the growing channel wing respectively to obtain a spliced ​​graph; The splicing graph is used to depict the cross-cutting stack, and the cross-cutting stack is the sand body model of the sandstone-mudstone interbed reservoir; The scatter plot is drawn with the sandstone thickness as the abscissa and the effective thickness as the ordinate; The method for drawing the identification standard line comprises: Performing linear regression fitting on all scattered points in the scatter plot to obtain a first identification standard line; The second identification standard line is obtained by taking the ratio of the average effective thickness to the average sandstone thickness as the slope; Above the identification standard line is the possible development area of ​​the columnar sand body; The method for establishing the well-layer coordinate system comprises: Select several wells in the area where the columnar sand bodies may develop; The well point position of the well is taken as the horizontal axis coordinate point of the coordinate system, and the top interface of the stratum vertically crossed by the well is taken as the vertical axis coordinate point of the coordinate system; The method of superimposing the well-layer coordinate system and the reservoir cross-section diagram comprises: Drawing a reservoir cross-section map in the well-layer coordinate system according to the reservoir interpretation results; During the drawing process, the well-layer coordinate system is made to completely correspond to the wells and layers in the reservoir cross-section diagram to complete the mutual superposition; The methods of describing the inherited channel core and the growing channel wing in an envelope manner include: On the superimposed well-layer coordinate system and reservoir profile, all inherited channel cores and growth channel wings are marked; Enveloping the calibrated inherited channel core and the growth channel wing to depict the inherited channel core and the growth channel wing; The enveloping method comprises: Enveloping the inherited channel core and the growing channel wing by a rectangular outline; During the enveloping process, the four sides of the rectangle intersect with the sand body respectively, and the sand body is inside the rectangle.

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