CN114991753A - Target point prediction method for horizontal well geosteering under variable azimuth condition - Google Patents

Abstract

The invention discloses a target point prediction method under a horizontal well geosteering azimuth changing condition, which comprises the steps of respectively calculating the vertical distance between each marker layer and the central line of a target window of a horizontal section by identifying a rock electric marker layer before target entering; calculating a stratum view dip angle according to the vertical depth difference of the two actually drilled marker layers, the plane distance and the vertical thickness between the two marker layers of the adjacent well or the pilot hole well; reading the plane position points of any two mark layers, connecting and extending the plane position points of the two mark layers, intersecting an isoline constructed by the position of the target point as the equivalent position of the target point, and measuring the linear distance between the plane position point of one mark layer and the equivalent target point; and based on the equal-thickness geological model, the sag of the selected mark layer plane position point, the formation dip angle, and the plane distance between the intersection point and the selected plane position point are utilized to complete the prediction of the sag of the target point. According to the method, the target prediction precision can be improved, the well bore smoothness of the horizontal well is effectively improved, and the subsequent accurate landing and horizontal section control of the horizontal well are guaranteed.

Description

Target point prediction method for horizontal well geosteering under variable azimuth condition

Technical Field

The invention belongs to the technical field of oil-gas exploration and development, and particularly relates to a target point prediction method under a horizontal well geosteering azimuth-varying condition.

Background

In an area with relatively low exploration degree, the depth of a designed target point has certain error due to the complex underground geological conditions and the limitation of seismic data interpretation precision, and the target point needs to be timely adjusted according to real drilling data in the real drilling process. Due to the successful application of a high build-up rate tool, most of the existing horizontal wells finish the torsion azimuth work when drilling to the vicinity of a target point, namely the track azimuth is continuously changed before entering the target, so that the target point vertical depth cannot be accurately predicted according to actual drilling data in the actual drilling process.

At present, two methods are generally adopted at home and abroad aiming at target point prediction under the condition of variable azimuth in the drilling process. One method comprises the steps of obtaining a single-well average speed curve through fine well seismic calibration, establishing a three-dimensional space average speed field, obtaining a target layer depth structural diagram through time-depth conversion, and predicting the vertical depth of a target point; and the other method is that before drilling, the rock electric marker layer of the adjacent well or the pilot hole well before entering the target is identified, and then the well deviation range of each rock electric marker layer during drilling is calculated by combining the design of the well track and the deviation capability of the directional tool. In the actual drilling process, the track is controlled in a segmented mode according to the well inclination range of each rock electric marker layer calculated in advance, and the aim of target centering is achieved. Both of the above two methods have certain limitations in the practical application process. The former has higher requirements on the curve quality and the seismic data quality, the target point prediction precision is difficult to meet the production requirement, and the latter inevitably causes poor smoothness of a borehole trajectory due to sectional control, thereby causing certain risks for later engineering construction.

Disclosure of Invention

The invention relates to a target point prediction method under a variable azimuth condition in horizontal well geosteering. The target point prediction method can effectively predict the target point under the variable azimuth condition in the drilling process of the horizontal well, improve the target point prediction precision, effectively improve the well smoothness of the horizontal well and provide guarantee for subsequent accurate landing and horizontal segment control of the horizontal well.

The invention adopts the following technical scheme: a target point prediction method for horizontal well geosteering under variable azimuth conditions comprises the following steps:

s1, identifying rock electric marker layers before entering the target based on analysis and comparison of adjacent wells or pilot wells, and respectively calculating the vertical distance between each marker layer and the central line of the target window of the horizontal section;

s2, calculating the formation dip angle according to the vertical depth difference and the plane distance of the two actually drilled marker layers and the vertical thickness between the two marker layers of the adjacent well or the pilot hole well;

s3, reading the plane position points of any two marker layers, connecting and extending the plane position points of the two marker layers, intersecting with the contour line constructed by the target point position, and measuring the linear distance between the plane position point of one marker layer and the intersecting intersection point;

and S4, based on the equal-thickness geological model, the sag of the selected mark layer plane position point, the formation dip angle, and the plane distance between the intersection point and the selected plane position point are utilized to complete the prediction of the sag of the target point.

And further, repeating the first step, the second step, the third step and the fourth step according to the drilling meeting mark layer in sequence, and predicting the depth of the target point in a rolling mode.

Further, the formula for calculating the formation apparent dip angle is as follows:

a＝argtan[|h-h ₁ |/L]

wherein h is the vertical thickness between two mark layers of the pilot hole well or the adjacent well; h1 is the vertical depth difference of the two mark layers of the real diamond; l is the plane distance of the two mark layers of the actual drill.

Further, the target point vertical depth formula is expressed as:

H＝H1+h+S*tan(a)

h1 is the vertical depth of the plane position point of one selected marker layer in the two selected marker layers, H is the vertical distance between the adjacent well or pilot hole and the target center, and S is the plane distance between the intersection point and the selected plane position point.

The invention has the beneficial effects that: the target prediction precision can be improved, the well smoothness of the horizontal well can be effectively improved, and the follow-up accurate landing and horizontal segment control of the horizontal well are guaranteed.

Drawings

FIG. 1 is a schematic flow diagram of a target point prediction method under a variable azimuth condition in horizontal well geosteering provided by the invention.

FIG. 2 is a schematic diagram of the position of a well rock electrical marker layer and the distance from a target center in the target prediction method under the variable azimuth condition in horizontal well geosteering provided by the invention.

FIG. 3 is a schematic diagram of the apparent dip angle of the stratum calculated by different stratum attitude in the target prediction method under the variable azimuth condition in horizontal well geosteering provided by the invention.

FIG. 4 is a schematic diagram of the position settings of the plane position points, the intersection points and the target points of two marker layers selected in the target point prediction method under the condition of variable azimuth in horizontal well geosteering provided by the invention.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 shows a target prediction method for horizontal well geosteering under variable azimuth conditions, which comprises the following steps:

identifying rock electric marker layers before entering the target based on analysis and comparison of adjacent wells or pilot wells, and respectively calculating the vertical distance between each marker layer and the central line of the target window of the horizontal section; as shown in FIG. 2, the positions of the electrical marker layers of the downhole rock and the distance from the target center are given according to different stratum pay states. In the subsequent calculation process, the numerical values can be directly adopted for calculation.

Calculating a stratum view dip angle according to the vertical depth difference of the two actually drilled marker layers, the plane distance and the vertical thickness between the two marker layers of the adjacent well or the pilot hole well;

reading the plane position points of any two marker layers, connecting and extending the plane position points of the two marker layers, intersecting with an isoline constructed by the target point position, and measuring the linear distance between the plane position point of one marker layer and the intersected intersection point;

and based on the equal-thickness geological model, the sag of the selected mark layer plane position point, the formation dip angle, and the plane distance between the intersection point and the selected plane position point are utilized to complete the prediction of the sag of the target point.

The pilot hole well is a well which is drilled for taking accurate data, determining an accurate layer and serving as a foundation for horizontal section construction under the condition that the geological conditions of the well position are not known, and aims to know the lithology, physical property, electrical property, oil-bearing property, oil-water relation of an oil-gas reservoir, structural condition and changes of the oil-water relation so as to determine target point parameters of horizontal wells such as A and B … and the like and play a role in correcting and designing target points. But its main role is to correct the location of target a (which is the starting point of the horizontal section of the horizontal well). The pilot borehole can be a straight pilot borehole or an inclined pilot borehole. The straight pilot hole is far away from the target A, and the straight pilot hole cannot meet the requirement under the condition of relatively complex geological conditions and needs to be inclined.

And further, repeating the first step, the second step, the third step and the fourth step according to the drilling encounter mark layer in sequence, and predicting the depth of the target point in a rolling mode.

Further, the formula for calculating the formation apparent dip angle is as follows:

a＝argtan[|h-h ₁ |/L]

wherein h is the vertical thickness between two mark layers of the pilot hole well or the adjacent well; h1 is the vertical depth difference of the two mark layers of the real diamond; l is the plane distance of the two mark layers of the actual drill.

As shown in fig. 3, under an actual formation attitude, the thickness of the vertical thickness between any two marker layers of the pilot hole well or the adjacent well and the vertical depth of the two actually drilled marker layers are uncertain, as shown in the landform on the left and right sides in fig. 3, the vertical thickness between any two marker layers of the pilot hole well or the adjacent well in the left side diagram is greater than the vertical depth of the two actually drilled marker layers, while in the right side diagram, the vertical thickness between any two marker layers of the pilot hole well or the adjacent well in the left side diagram is less than the vertical depth of the two actually drilled marker layers, and when the formation dip angle is actually calculated, the absolute value of the difference between the vertical thickness between any two marker layers of the pilot hole well or the adjacent well and the vertical depth of the two actually drilled marker layers is taken for calculation.

As shown in fig. 4, the two selected plane position points of the two marker layers are represented as B1 and B2, which connect B1 and B2, and after the connecting line is extended, the connecting line intersects with the contour line of the target point position structure, the intersection point is set as a ', and the linear distance between the marker layer where the measurement plane position point B2 is located and the intersection point a' is set as S. And based on the equal-thickness geological model, the vertical depth of the target point A is predicted by utilizing the vertical depth of the point B2, the apparent dip angle of the stratum, and the plane distance between the intersection point A' and the point B2.

Further, the target point vertical depth formula is expressed as:

H＝H1+h+S*tan(a)

h1 is the vertical depth of the plane position point of one selected marker layer in the two selected marker layers, H is the vertical distance between the adjacent well or pilot hole and the target center, and S is the plane distance between the intersection point and the selected plane position point.

The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.

Claims (4)

1. A target point prediction method for horizontal well geosteering under variable azimuth conditions is characterized by comprising the following steps:

s1, identifying rock electric marker layers before entering the target based on analysis and comparison of adjacent wells or pilot wells, and respectively calculating the vertical distance between each marker layer and the central line of the target window of the horizontal section;

s2, calculating the formation dip angle according to the vertical depth difference and the plane distance of the two actually drilled marker layers and the vertical thickness between the two marker layers of the adjacent well or the pilot hole well;

s3, reading the plane position points of any two marker layers, connecting and extending the plane position points of the two marker layers, intersecting with the contour line constructed by the target point position as an equivalent target point, and measuring the linear distance between the plane position point of one marker layer and the equivalent target point;

and S4, based on the equal-thickness geological model, the sag depth of the selected plane position point of the mark layer, the dip angle of the stratum, and the plane distance between the intersection point and the selected plane position point are utilized to complete the prediction of the sag depth of the target point.

2. The target point prediction method for the horizontal well geosteering in the variable azimuth condition according to claim 1, wherein the first step, the second step, the third step, the fourth step and the target point depth prediction are repeated in sequence according to drilling and encountering mark layers, and target point depth is predicted in a rolling mode.

3. The method for predicting the target point under the variable azimuth condition in the horizontal well geosteering according to claim 1, wherein the calculation formula of the formation apparent dip angle is as follows:

a＝argtan[|h-h ₁ |/L]

wherein h is the vertical thickness between two mark layers of the pilot hole well or the adjacent well; h1 is the vertical depth difference of the two mark layers of the real diamond; l is the plane distance of the two mark layers of the actual drill.

4. The method for predicting the target point under the variable azimuth condition in the horizontal well geosteering according to claim 1, wherein the target point vertical depth formula is as follows:

H＝H1+h+S*tan(a)

h1 is the vertical depth of the plane position point of one selected marker layer in the two selected marker layers, H is the vertical distance between the adjacent well or pilot hole and the target center, and S is the plane distance between the intersection point and the selected plane position point.

Images