Method for correcting dip angle of deep tight gas reservoir horizontal well while drilling

Abstract

The invention belongs to the technical field of horizontal well geological seismic steering, and discloses a method for correcting a stratigraphic dip angle while drilling of a deep tight gas reservoir horizontal well. The method for correcting the stratigraphic dip angle while drilling of the deep tight gas reservoir horizontal well is established by fully considering influence factors of equipment types while drilling and oil reservoir types and combining seismic interpretation and key parameters of data while drilling, so that the problems of how to ensure that a horizontal section penetrates through a reservoir stratum to the maximum extent and how to correct the stratigraphic dip angle while drilling in an existing geosteering technology are solved. According to the seismic geosteering, the prediction precision and the working efficiency of horizontal well target entering are remarkably improved, horizontal well steering work can be effectively guided, and whether the horizontal well can achieve the design purpose or not and the productivity of the horizontal well are directly related.

Description

Technical Field

[0001] The invention belongs to the technical field of geological seismic guidance of horizontal wells, and the invention relates to a method for correcting formation dip while drilling a horizontal well of a deep tight gas reservoir. Background Art

[0002] A horizontal well is a special directional well in which the drill bit trajectory enters the oil and gas layer along the oil and gas layer's inclination and occurrence. It is generally believed that the maximum wellbore inclination angle is not less than 86°. It can effectively increase the leakage area of ​​the oil and gas layer and improve the oil and gas recovery rate. It is one of the effective means to increase production. Geosteering technology refers to the technology of monitoring and controlling the wellbore trajectory based on the establishment of geological models, based on the logging while drilling technology, combined with engineering technologies such as logging and drilling. It integrates reservoir geology, logging, engineering technology and computers to ensure that the actual wellbore passes through the reservoir and obtains the best position, thereby maximizing the drilling rate and development benefits of the oil and gas layer. Geosteering originally belonged to the category of drilling, and was mainly used for the measurement of engineering parameters such as well inclination, azimuth, torque, etc. while drilling. With the continuous development and combination of drilling and logging technology, especially since the 1990s, instruments such as resistivity, formation density, neutron porosity, acoustic wave, and wellbore diameter have gradually been drilled while drilling, changing the situation of wired logging or post-drilling logging, and greatly improving the timeliness and effectiveness of logging while drilling evaluation.

[0003] It is difficult to understand and develop deep tight gas reservoirs. Among them, Changling Gas Field is the first large-scale integrated structural lithology composite gas reservoir in my country that integrates high CO2 content, volcanic rocks and tight sandstones. It has the characteristics of high CO2 content, deep reservoir burial, and poor physical properties. The large-scale application of horizontal wells and volume fracturing are strategic measures for the development of Jilin Oilfield. In the exploration stage, favorable areas are selected, demonstration areas are established, and comprehensive implementation has broad prospects. Grasp the real situation, do a good job, and gain experience and results to promote the construction of tens of millions of tons of oilfields as scheduled.

[0004] To improve the quality of horizontal wells hitting the target, three key points and one key point are to be timely.

[0005] There are three key points: first, the depth of the target point, which is calculated by stratum calibration and known well depth to design the well depth; second, the size of the formation dip, which is mainly predicted by reservoir profile, seismic profile and depth calculation while drilling; third, the lateral change of the reservoir, which is mainly achieved by using seismic attributes and inversion techniques. There are currently two main methods used in the market: (1) The time domain profile is converted into a depth domain profile through processing, and on this basis, the true formation dip is directly calculated from the depth of horizontal well drilling and the seismic profile; (2) In the time domain profile, the time difference between the upper and lower layers is converted into a depth value, the distance value is read and the dip is calculated; in this case, multiple geologists and geophysical personnel are required to cooperate with each other, and the velocity spectrum data obtained through seismic processing is converted into the average velocity using the Dix formula, and the regional velocity field is established. The time domain data is converted into the depth domain data, and the true formation dip, well trajectory and altitude are calculated. There are many problems such as long time consumption and errors caused by inaccurate velocity picking. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for correcting the formation dip while drilling a horizontal well in a deep tight gas reservoir. The method fully considers the influencing factors of the type of drilling equipment and the type of reservoir, combines seismic interpretation and key parameters of drilling data, and establishes a method for correcting the formation dip while drilling a horizontal well in a deep tight gas reservoir, thereby solving the problem of how to ensure that the horizontal section penetrates the reservoir to the maximum extent in the existing geological guidance technology. This seismic geological guidance significantly improves the prediction accuracy and work efficiency of horizontal well targeting, can effectively guide the guidance work of horizontal wells, and is directly related to whether the horizontal well can achieve the design purpose and the level of horizontal well production capacity.

[0007] The above object of the present invention is achieved through the following technical solutions:

[0008] A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir comprises the following steps:

[0009] (1) Information acquisition before entering the target well: Obtain the type of drilling equipment. Different types of reservoirs have different requirements for the accuracy of guidance equipment. Currently, the MWD (Measurement While Drilling) equipment is widely used in the market. During the exploration and development of oil and gas fields, logging must be carried out after drilling in order to understand the rare conditions of the bottom layer. Using the logging while drilling technology, the drilling parameters and formation parameters measured are used to adjust the drill bit trajectory in time to make it drill along the target layer. Since the formation parameters obtained by the logging while drilling are the formation parameters just drilled, they are closest to the original state of the formation. It is more beneficial for evaluating the oil and gas content of complex formations than general cable logging; collect dynamic and static information such as the seismic datum level, high point altitude, and well location information of the wells drilled in the area, core filling, well trajectory, stratification, logging (including acoustic time difference curve, natural gamma curve, natural potential and resistivity curve) and logging (lithology and oil and gas content information) of all seismic work areas;

[0010] (2) Load the seismic work area and well information, and convert the acoustic time difference curve into seismic wave impedance information by making synthetic seismic records, and finely calibrate the wells and seismic lines. Through the local stable marker layers that have been clearly defined in the study area, such as the widely developed gravel layer or mudstone layer, the wave impedance difference between the upper and lower sandstone layers will be generated, and strong peaks or troughs will be formed on the seismic profile. It can also be compared with the large unconformity surface in the region, and obvious onlap, onlap and truncation will also be formed on the seismic profile. By converting the single well logging information with higher vertical resolution into seismic information with higher lateral resolution, if the compliance rate exceeds 80%, the next step can be carried out; otherwise, recalibrate and iterate repeatedly until the compliance rate exceeds 80%;

[0011] (3) Using 2D and 3D seismic interpretation, calculate the formation dip of the target layer according to Formula 1: True formation dip = 90-DEGREES [ATAN (vertical distance / horizontal distance)] and the possible range is plus or minus 10 degrees;

[0012] (4) During the drilling process, the MWD (Measurement While Drilling) equipment is currently widely used in the market. During the exploration and development of oil and gas fields, logging must be carried out after drilling in order to understand the rare conditions of the bottom layer. Using the logging while drilling technology, the drill bit trajectory is adjusted in time using the measured drilling parameters and formation parameters to make it drill along the target layer. Since the formation parameters obtained by logging while drilling are the formation parameters just drilled, they are closest to the original state of the formation. It is more beneficial for evaluating the oil and gas content of complex formations than general cable logging. It collects dynamic and static information such as the seismic datum level, high point altitude, and well location information of the wells drilled in the area, core filling, well trajectory, stratification, logging (including acoustic time difference curve, natural gamma curve, natural potential and resistivity curve) and logging (lithology and oil and gas content information) in all seismic work areas, and obtains the drilling inclination, gamma, resistivity and logging lithology, and compares the actual drilling marker layer depth with the designed marker layer depth on site;

[0013] (5) Compare and correct the well trajectory, calculate the well trajectory according to Formula 2 (Formula 2: Well trajectory = SIN ((90-(well deviation 2 + well deviation 1) / 2) / 180*3.1415926)*(depth measurement 2-depth measurement 1) + vertical depth for calculation), update the well trajectory, and provide a basis for accurate target entry in the next step of drilling;

[0014] (6) Through continuous revision, the consistency between the designed trajectory and the drilling results is ensured, making the prediction of the target layer more accurate.

[0015] Before the step (4), it is necessary to calculate the corresponding target point and target layer information according to formula 2, where formula 2 is: well trajectory = SIN ((90-(well deviation 2 + well deviation 1) / 2) / 180*3.1415926)*(depth 2-depth 1)+vertical depth for calculation; altitude = altitude H(Z)-vertical depth, and the well trajectory is obtained.

[0016] The present invention also seeks to protect the on-site application of a method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir provided by the present invention in Dehui area.

[0017] The beneficial effects of the present invention compared with the prior art are:

[0018] The present invention provides a method for correcting formation dip while drilling a horizontal well in a deep and tight gas reservoir. By fully considering the influencing factors of the type of drilling equipment and the type of oil reservoir, the calculation method of the formation dip while drilling is considered for the first time and introduced into the horizontal well while drilling guidance technology. Combining seismic interpretation and key parameters of drilling data, a method for correcting formation dip while drilling a horizontal well in a deep and tight gas reservoir is established. This seismic geological guidance significantly improves the prediction accuracy and work efficiency of horizontal well targeting. At the implementation site in Dehui area, the prediction accuracy of horizontal well targeting is increased from 50% to 75%, the reservoir drilling rate is 80%, and the gas layer drilling rate is 85%; only one geologist and geophysical prospector is needed at the horizontal well guidance site, saving 60 hours of work time, which can effectively guide the horizontal well guidance work. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The figure shows the directional geological model diagram of the horizontal well of Changshen 47 well in the example of the present invention;

[0021] Figure 2 The figure shows the predicted trajectory of the horizontal well guide well of the Changshen 47 well in the example of the present invention;

[0022] Figure 3 Shown is a trajectory tracking diagram of the horizontal well guide well of Changshen 47 well in the example of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0024] Example 1

[0025] Reference Figure 1 This specific embodiment adopts the following technical solution: A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir, comprising the following steps:

[0026] Step 1: Obtain the type of equipment while drilling. Different types of reservoirs have different requirements for the accuracy of guidance equipment. Currently, the MWD (Measurement While Drilling) equipment is widely used in the market. During the exploration and development of oil and gas fields, logging must be carried out after drilling in order to understand the rare conditions of the bottom layer. Using the logging while drilling technology, the drilling parameters and formation parameters measured are used to adjust the trajectory of the drill bit in time to make it drill along the direction of the target layer. Since the formation parameters obtained by logging while drilling are the parameters of the formation just drilled, they are closest to the original state of the formation. It is more beneficial for evaluating the oil and gas content of complex formations than general cable logging; collect the seismic datum level, high point altitude and well location information of the wells drilled in the area, core filling, well trajectory, stratification, logging (including acoustic time difference curve, natural gamma curve, natural potential and resistivity curve) and logging (lithology and oil and gas content information) and other dynamic and static data of all seismic work areas;

[0027] The present invention takes the Changshen 47 well in the Changling fault depression of the Songliao Basin as an example;

[0028] Step 2: If Figure 1 As shown, load the seismic work area and well information, convert the acoustic time difference curve into seismic wave impedance information by making synthetic seismic records, finely calibrate the well seismic, and convert the single well logging information with high vertical resolution into seismic information with high lateral resolution by comparing the local stable marker layers (such as the widely developed conglomerate layers or mudstone layers, which produce wave impedance differences with the upper and lower sandstone layers) and the regional large unconformity surface in the study area. If the coincidence rate exceeds 80%, proceed to the next step, otherwise recalibrate and iterate repeatedly until the coincidence rate exceeds 80%; comprehensively check the consistency between the designed trajectory and the structure and seismic profile; clarify the local stable and unstable marker layers;

[0029] Step 3: If Figure 2 As shown in the figure, the formation dip of the target layer is calculated by using 2D and 3D seismic interpretation. Formula 1 is: true formation dip = 90-DEGREES [ATAN (vertical distance / horizontal distance)] and the possible range is plus or minus 10 degrees. The well trajectory is compared and corrected; if it is inconsistent with the actual drilling result, it is promptly modified to the calculated well trajectory (Formula 2 is well trajectory = SIN ((90-(well deviation 2 + well deviation 1) / 2) / 180*3.1415926)*(depth measurement 2-depth measurement 1) + calculation vertical depth), and the well trajectory is updated to provide a basis for the next step of drilling to accurately enter the target.

[0030] The Changshen 47 well was drilled to 5058 meters (4847.9 meters vertical depth), with a predicted well inclination of 880 and a possible range of -10 to +10;

[0031] Step 4: During the drilling process, the MWD (Measurement While Drilling) equipment is currently widely used in the market. During the exploration and development of oil and gas fields, logging must be carried out after drilling in order to understand the rare conditions of the bottom layer. Using the logging while drilling technology, the drilling parameters and formation parameters measured are used to adjust the drill bit trajectory in time to make it drill along the target layer. Since the formation parameters obtained by logging while drilling are the formation parameters just drilled, they are closest to the original state of the formation. It is more beneficial to evaluate the oil and gas content of complex formations than general cable logging; collect the seismic datum level, high point altitude and well location information of the wells drilled in the area, core filling, well trajectory, layering, logging (including acoustic time difference curve, natural gamma curve, natural potential and resistivity curve) and logging (lithology and oil and gas content information) of all seismic work areas to obtain the drilling inclination, gamma, resistivity and logging lithology, and compare the actual drilling marker layer depth with the designed marker layer depth;

[0032] The measured point of Changshen 47 well is 5029.25 meters (vertical depth 4846.68 meters), and the measured well inclination is 86.80.

[0033] Step 5: Compare and correct the well trajectory; if it is inconsistent with the actual drilling results, modify it in time. Calculate the well trajectory (Formula 2: Well trajectory = SIN ((90-(well deviation 2 + well deviation 1) / 2) / 180*3.1415926)*(depth measurement 2-depth measurement 1) + vertical depth for calculation), update the well trajectory, and provide a basis for the next step of drilling to accurately enter the target.

[0034] Step 6: Through continuous correction, the consistency of the designed trajectory and the drilling results is ensured, making the prediction of the target layer more accurate. Before step 4, the corresponding target point and target layer information need to be calculated, where formula 1: true formation inclination = 90-DEGREES [ATAN (vertical distance / horizontal distance)]; formula 2: well trajectory = SIN ((90-(well inclination 2 + well inclination 1) / 2) / 180*3.1415926)* (depth measurement 2-depth measurement 1) + calculation vertical depth; altitude = altitude H (Z)-vertical depth, and the well trajectory is obtained.

[0035] Changshen 47 well recorded relatively continuous high gas logging at 5041-5058 meters (vertical depth 4847.28-4847.94 meters).

[0036] The present invention establishes a method for correcting formation dip while drilling a horizontal well in a deep and tight gas reservoir. For the first time, the calculation method for correcting formation dip while drilling is introduced into the horizontal well while drilling guidance technology. At the same time, the seismic interpretation and drilling data (natural potential, natural gamma, resistivity) are combined to judge the entry into the sandstone layer, thereby obtaining the depth of the target layer (depth measurement and vertical depth), and then calculating the true formation dip, well trajectory and altitude parameters. A method for correcting formation dip while drilling a horizontal well in a deep and tight gas reservoir is established. This seismic geological guidance can effectively improve the prediction accuracy and work efficiency of horizontal well targeting. At the implementation site in Dehui area, the prediction accuracy of horizontal well targeting was improved from 50% to 75%, the reservoir drilling rate was 80%, and the gas layer drilling rate was 85%. Only one geologist and geophysical prospector are required at the horizontal well guidance site, saving 60 hours of work, which has important scientific guiding significance for horizontal well guidance technology.

[0037] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir, characterized in that: The steps include: (1) Information acquisition before entering the target; (2) Loading the seismic work area and well information, converting the acoustic time difference curve into seismic impedance information by making synthetic seismic records, and fine well calibration. Through the local stable marker layer that has been clearly defined in the study area, the widely developed conglomerate layer or mudstone layer, and the upper and lower sandstone layers, a wave impedance difference will be generated, which will form a strong peak or trough on the seismic profile; compared with the large unconformity surface in the region, it will also form obvious onlap, underlap, and truncation phenomena on the seismic profile; (3) Using 2D and 3D seismic interpretation, calculate the stratigraphic dip of the target layer; (4) Using logging while drilling technology, the drill bit trajectory is adjusted in time using the measured drilling parameters and formation parameters to make the drill advance along the target layer, and collect the seismic datum, high point altitude and well location information, core patching, well trajectory, layering, logging and dynamic and static information of all wells drilled in the seismic work area; (5) Compare and correct well trajectories; (6) Ensure that the designed trajectory is consistent with the drilling results through continuous revision.

2. A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir as claimed in claim 1, characterized in that: In step 1), the seismic datum, high point altitude, well location information, core patching, well trajectory, layering, well logging and dynamic and static information of all the wells drilled in the seismic work area are collected.

3. The method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir according to claim 1, characterized in that: In step 1), information is collected through the MWD equipment.

4. The method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir according to claim 1, characterized in that: In step 2), by converting the single well logging information with higher vertical resolution into seismic information with higher lateral resolution, if the coincidence rate exceeds 80%, the next step can be carried out; Otherwise, recalibrate and iterate repeatedly until the compliance rate exceeds 80%.

5. A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir as claimed in claim 4, characterized in that: In step 3), the formation inclination of the target layer is calculated according to formula 1. Formula 1 is: true inclination of formation = 90-DEGREES [ATAN (vertical distance / horizontal distance)].

6. A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir as claimed in claim 5, characterized in that: In step 4), the wellbore inclination, gamma, resistivity and logging lithology are obtained while drilling, and the actual drilling marker layer depth is compared with the designed marker layer depth.

7. A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir as claimed in claim 6, characterized in that: In step 5), the well trajectory is calculated according to formula 2: Formula 2 is: Well trajectory = SIN ((90-(well deviation 2 + well deviation 1) / 2) / 180*3.1415926)*(depth 2-depth 1)+vertical depth for calculation); Update the well trajectory to provide a basis for accurate targeting of the well to be drilled.

8. A method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir as claimed in claim 7, characterized in that: Before step (4), the corresponding target point and target layer information need to be calculated according to formula 2, where formula 2 is: well trajectory = SIN ((90-(well deviation 2+well deviation 1) / 2) / 180*3.1415926)*(depth measurement 2-depth measurement 1)+vertical depth for calculation; Altitude = altitude H(Z) - vertical depth, and the well trajectory is obtained.

9. Application of the method for correcting formation dip while drilling a horizontal well in a deep tight gas reservoir as described in any one of claims 1 to 8 in the field in Dehui area.

Images