A shale gas prospective area investigation well site deployment method

Abstract

The present application provides a kind of shale gas prospective area investigation well site deployment method, belong to rock gas well site deployment technical field, solve the strong multi-solution of shale gas target layer prediction in prior art, shale target layer prediction is not accurate and the problem of cost control.It includes the following steps: according to the target area of prospective area geological survey evaluation, combined with regional tectonic geological conditions, based on the method of cost-probing geological target effect deployment wide area electromagnetic profile;Collect adjacent or adjacent well logging or formation electromagnetic information, establish electromagnetic-geological interpretation model, analyze stratigraphic lithology electromagnetic difference at the same time, propose interpretation marker bed;Combined with geological background, adjacent geophysical line, drilling data form wide area electromagnetic method comprehensive geological interpretation method, while removing multi-solution, interpret the shale burial depth of target layer, distribution geological information.Using wide area electromagnetic method and comprehensive various geological, geophysical information to remove multi-solution, accurately, low cost deployment investigation well site.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of shale gas well site deployment, and particularly relates to a shale gas prospective area investigation well site deployment method. BACKGROUND

[0002] A shale gas prospective area is an area with shale gas exploration potential selected through small-scale shale gas geological investigation in the early stage. Basic maps such as sedimentary facies maps, shale isopach maps, and organic carbon content distribution maps of the target layer are prepared in the area, but the exploration degree of the area is low, the shale gas content, shale electrical properties and other parameters are unclear, there is no or only a small amount of two-dimensional seismic data in the area, and there are limited reference data from adjacent wells. In order to quickly obtain the stratigraphic sequence of the shale target layer, the real rock core in the well, and the geological parameters and logging electrical parameters such as shale thickness, organic carbon content, maturity, shale reservoir properties, and shale gas content, it is necessary to deploy shale gas geological investigation wells (generally using a wireline coring drill) to further delineate the favorable area and deploy exploration parameter wells on the basis of the progress made in the investigation wells, so as to promote shale gas block optimization and commercial exploration.

[0003] The previous method of deploying investigation wells in a shale gas prospective area is based on two-dimensional seismic geophysical exploration methods, but there are difficulties in deploying two-dimensional seismic drilling in the shale gas prospective area in the south: (1) there is no two-dimensional seismic coverage in the shale gas prospective area; (2) there is two-dimensional seismic coverage, but there is a certain distance from the deployment target area, and the cost of redeploying two-dimensional seismic is high; (3) some older two-dimensional seismic data has poor quality; (4) the terrain in the southern region is undulating and karst is developed, and the terrain, karst caves and fractures have a strong absorption attenuation and energy shielding effect on seismic signals, resulting in poor quality of newly collected two-dimensional seismic data and large errors in forced well deployment, so there is an urgent need for a low-cost geophysical investigation well deployment method suitable for special geological conditions in the south.

[0004] Wide-field electromagnetic method (WFEM) is a kind of artificial source electromagnetic exploration method developed rapidly in recent years, mainly adopting E-E working mode, that is, adopting electrical source and receiving electric field mode, and its main basis is electrical property, that is, apparent resistivity difference for geological layering, fault identification and the like, and the wide-field electromagnetic method has the characteristics of low cost and strong practicability in complex terrain area or karst area. In recent years, the F-E wide-field electromagnetic method is applied more and more in oil and gas, mineral, geothermal, hydrology, engineering and the like. Academician He Jishan of Central South University proposes a method and device for identifying shale gas sweet spot area (publication number CN104656157B) by using the wide-field electromagnetic method, shale burial depth, thickness and shale lateral distribution are obtained according to underground formation electromagnetic difference by the method and device, and are not affected by surface karst shielding, which provides important geological information and basis for large-scale exploration and development of shale gas. The method is mainly based on electromagnetic information of a target area, and shale gas sweet spot area is predicted by inversion research to establish an interpretation model, but the method has strong multi-solution problem in practical application due to many geological factors causing high resistance or low resistance, and the actual geological background and other geophysical data are not considered for removing the multi-solution problem; in addition, the method is difficult to distinguish the similar formation combination of the target layer and the upper and lower layers of the target layer, and the identification precision of the wide-field electromagnetic method is relatively poor compared with the seismic technology, shale burial depth, thickness and shale lateral distribution prediction are inaccurate; in addition, the method does not mention how to deploy well position by using limited wide-field geophysical lines under the condition of cost control. Therefore, a shale gas prospective area investigation well position deployment method based on the wide-field electromagnetic method and removing multi-solution by comprehensively considering various geological and geophysical information is needed. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a shale gas prospective area investigation well position deployment method, which uses the wide-field electromagnetic method and removes multi-solution by comprehensively considering various geological and geophysical information to accurately and low-cost deploy investigation well position.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A shale gas prospective area investigation well position deployment method, comprising the following steps:

[0008] S1: first, according to the target area of the prospective area geological investigation and evaluation, combining with the regional tectonic geological conditions, deploying the wide-field electromagnetic profile based on the cost-prospecting geological target effect method;

[0009] S2: collecting adjacent well logging or formation electromagnetic information or adjacent well logging or formation electromagnetic information, establishing an electromagnetic-geological interpretation model, analyzing the formation lithology electromagnetic difference, and proposing an interpretation marker layer;

[0010] S3: Combined with geological background, adjacent geophysical lines, drilling data, form a comprehensive geological interpretation method of wide area electromagnetic method, remove the multi-solution at the same time, interpret the shale depth of the target layer, distribution geological information;

[0011] S4: According to the interpretation of the geological profile of the target layer depth, distribution characteristics, combined with the structure preservation condition, surface drilling construction condition, and considering the drilling budget, the well site of the investigation well is deployed.

[0012] Preferably, in step S1, through the shale gas basic geological survey and sampling of the prospective area, various shale gas maps are prepared, and the drilling target area is screened according to the selection and evaluation procedure.

[0013] Preferably, the method for cost-probing geological target effect comprises:

[0014] S11: Deploying geophysical lines vertically along regional structure lines;

[0015] S12: Starting from the outcrop point of the target layer to the deep buried area;

[0016] S13: The geophysical line passes through the intended drilling target point selected by geological survey;

[0017] S14: The length of the geophysical line is controlled by the regional structure near the intended drilling target point;

[0018] S15: According to the practice, the wide area electromagnetic profile is used to deploy drilling, the point interval is 100m, the point interval near the intended drilling target point is 20m, and the single point acquisition time is at least 4 hours; after ensuring the quality of single point acquisition, controlling regional structure units and deploying geophysical lines for wells, unnecessary geophysical lines are not deployed.

[0019] Preferably, the specific steps of step S2 are:

[0020] S21: Resistivity test is performed on different strata rocks in the study area, and the resistivity difference of different lithology is analyzed. Under the condition of no water, the resistivity of carbonate rock is higher than that of shale;

[0021] S22: Analyze the resistivity logging curve of adjacent wells. The difference between carbonate rock and underlying shale is obvious, and the bottom boundary of carbonate rock is the marker bed;

[0022] S23: Directly collect single point MT resistivity curve at the well point position of adjacent well;

[0023] S24: According to the rock-electricity relationship curve, find out the marker bed, and establish an interpretation model.

[0024] Preferably, the specific steps of step S3 are:

[0025] S31: Based on the method provided by the wide-area electromagnetic manufacturer, one-dimensional and two-dimensional inversion of the wide-area profile is carried out, and the CAD software is used to realize the graphical display;

[0026] S32: Along the geophysical line, the ground geological survey is carried out, the surface route geological profile is prepared, the surface geological basis is provided for the geophysical interpretation, and the surface geological-underground wide-area profile comprehensive map is prepared;

[0027] S33: The wide-area inversion profile comprehensive geological interpretation is carried out in combination with the regional geological map, the ground route geological survey, the interpretation marker layer and the interpretation model.

[0028] Preferably, the specific steps of the step S33 are:

[0029] S331: The reliable marker layer and the obvious fault structure are preferentially interpreted; in combination with the ground route geological survey, the carbonate rock bottom boundary, the upper and lower electrical property change is large, the top and bottom are preferentially interpreted, the fault with obvious dislocation is preferentially interpreted; if there is a neighboring two-dimensional seismic profile near the wide-area profile, the wide-area interpretation is corrected according to the two-dimensional seismic, the overall trend of the stratum in the same tectonic background is grasped, and the marker layer stratum distribution trend corrected;

[0030] S332: The layer system with strong multi-solution needs to be combined with the surface geology, the regional stratum thickness and the lithological characteristics to exclude the multi-solution.

[0031] S333: For the purpose layer and the combination with the upper and lower stratum lithology, since the electrical property characteristics tend to be consistent, it is difficult to distinguish on the electromagnetic profile, and only the reasonable speculation of the layer position can be made through the regional stratum thickness when the geological horizon interpretation is carried out.

[0032] Preferably, the step S4 proposes the well site and the alternative well site suggestion according to the interpreted geological profile, in combination with the tectonic preservation condition, the surface drilling construction condition and the consideration of the drilling budget; and the stratum burial depth and the thickness of the pre-drilling well are calculated through the wide-area electromagnetic interpretation profile, and the pre-drilling columnar chart is prepared, so as to provide the basis for the survey well geology and the engineering design.

[0033] As described above, since the above technical scheme is adopted, the beneficial effects of the present application are:

[0034] The present application is based on wide-area electromagnetic method and removes multi-solution by synthesizing various geological and geophysical information, and accurately and low-costly deploys investigation well position; shale target layer stratigraphic sequence and downhole real core can be quickly obtained; and geological parameters such as shale thickness, organic carbon content, maturity, shale reservoir property and shale gas content and logging electrical property parameters can be obtained; so that on the basis of investigation well progress, favorable area can be further delineated, and exploration parameter well can be deployed, thereby promoting shale gas block optimization and commercial exploration; the method has great application prospect and plays an important role in promoting regional shale gas prospective area exploration. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and other related drawings can be obtained by those skilled in the art without creative labor on the premise of not paying creative labor.

[0036] Figure 1 The well position deployment method flow chart provided by the embodiments of the present application;

[0037] Figure 2 The shale gas prospective area selection evaluation flow chart provided by the embodiments of the present application;

[0038] Figure 3 The wide-area electromagnetic profile map deployed by the cost-prospecting geological target effect optimization method provided by the embodiments of the present application;

[0039] Figure 4 The resistivity test map of different strata rocks provided by the embodiments of the present application;

[0040] Figure 5 The MT data collected at the position of adjacent well drilling to establish an interpretation model map provided by the embodiments of the present application;

[0041] Figure 6 The one-dimensional wide-area electromagnetic profile map of inversion provided by the embodiments of the present application;

[0042] Figure 7 The two-dimensional wide-area electromagnetic profile map of inversion provided by the embodiments of the present application;

[0043] Figure 8 The ground geological-wide profile comprehensive interpretation map provided by the embodiments of the present application;

[0044] Figure 9 The wide-area geophysical geological interpretation profile and buried depth map provided by the embodiments of the present application. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0047] In the description of the present application, it should be noted that if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the application is used, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0048] The following will be described in detail Figures 1-9 The present application is described in detail.

[0049] Embodiment:

[0050] A shale gas prospective area investigation well site deployment method, as shown in Figure 1 , comprises the following steps:

[0051] S1: first, according to the target area of the prospective area geological investigation and evaluation, combining with the regional tectonic geological conditions, deploying a wide area electromagnetic profile based on the cost-prospecting geological target effect method; through the shale gas basic geological investigation and sampling in the prospective area, preparing various shale gas maps, and screening the drilling target area according to the selection and evaluation procedure, as shown in Figure 2 , the drilling target area is preferably selected;

[0052] The optimal deployment method based on the cost-prospecting geological target effect includes:

[0053] S11: deploying geophysical lines vertically along the regional tectonic line;

[0054] S12: starting from the surface outcrop point of the target layer and deploying to the deep buried area;

[0055] S13: The geophysical line is selected by geological survey to the intended drilling target point;

[0056] S14: The length of the geophysical line is controlled to the regional structure near the intended drilling target point as a principle;

[0057] S15: According to the practice, the wide area electromagnetic profile is used for deploying drilling, the acquisition point and point spacing is 100m, the point spacing is 20m in the vicinity of the intended drilling target point, and the single point acquisition time is at least 4 hours; after ensuring the single point acquisition quality, ensuring the control of the regional structure unit, and ensuring the deployment of the geophysical line, unnecessary geophysical lines are not deployed.

[0058] As shown in Figure 3 , the A area is a shale gas prospective area selected in the early stage, with an area of about 1000km 2 , the black shale of the Niutitang Formation of the Cambrian System is the target layer; the area has a certain shale gas working basis, stratigraphic profile measurement is carried out, and one shale gas geological survey well and one geothermal well are implemented, among which the shale gas well has a certain shale gas show, and in addition, one two-dimensional seismic profile is implemented; according to the evaluation procedure of the selected area, the drilling target area this time is mainly concentrated in the two wings of the Xingren syncline, according to the previous sedimentary facies analysis, the target layer and the overlying and underlying strata in the east wing and the west wing have phase change, which are two different drilling target areas, therefore, in order to accurately explore the shale gas geological characteristics of the syncline, one shale gas geological survey well is needed in the east wing and the west wing, and two wide area electromagnetic profiles are deployed according to the cost-probing geological target effect optimization method for the two targets, among which Figure 3 the middle B area GY19-1 is a wide area geophysical line deployed in the west of the syncline, which controls the outcrop point of the target layer, the secondary Xuanwei anticline, the intended drilling point, and is perpendicular to the regional structure line, with a length of 10km; Figure 3 the middle C area GY20-1 is a wide area geophysical line deployed in the east of the syncline, which controls the outcrop point of the target layer, the intended drilling point, and is perpendicular to the regional structure line, with a length of 7km.

[0059] S2: Collecting well logging or stratigraphic electromagnetic information of adjacent areas or adjacent wells, establishing electromagnetic-geological interpretation model, and analyzing stratigraphic lithology electromagnetic difference to propose interpretation marker layer;

[0060] The specific steps of step S2 are:

[0061] S21: Resistivity test is performed on different strata rocks in the study area, and resistivity difference of different lithology is analyzed, under the condition of no water, the resistivity of carbonate rock is higher than that of shale; as shown in Figure 4 , the resistivity of carbonate rock is much higher than that of shale;

[0062] S22: Analyzing the resistivity logging curve of the adjacent well, the difference between the carbonate rock of the Loumanguan Formation-Qingxidong Formation and the underlying shale is obvious, and the bottom boundary of the carbonate rock is the marker layer;

[0063] S23: Collecting single-point MT resistivity curves directly at the well point position of the adjacent well; Figure 5 In order to collect the geothermal well resistivity curves by using MT, the top and bottom of the Wuxun group are marker layers, and the upper and lower layers are low resistance, and the Wuxun group is high resistance;

[0064] S24: According to the rock-electricity relationship curve, the marker layer is found out, and the interpretation model is established; the layer group structure interpretation mode is established, which indicates the carbonate rock and clastic rock formation by using the vertically continuous high and low resistance electrical layers; the interpretation mode is established, which indicates the development of faults by using the upper and lower continuous layer interruption; the stratum electrical property test, the drilling resistivity curve and the MT resistivity curve above the drilling are comprehensively considered, and it is considered that the bottom boundary of the Loumanguan group-carbonate rock of the Qingxudong group and the top and bottom of the Wuxun group are marker layers.

[0065] S3: Combined with the geological background, the adjacent geophysical line and the drilling data, the comprehensive geological interpretation method of wide area electromagnetic method is formed, the multi-solution is removed, and the shale depth and distribution geological information of the target layer are interpreted;

[0066] The specific steps of step S3 are:

[0067] S31: Based on the method provided by the wide area electromagnetic manufacturer, the wide area profile one-dimensional and two-dimensional inversion is carried out, and the graphic display is realized by using the CAD software, as shown in Figure 6 and Figure 7 ;

[0068] S32: Along the geophysical line, the ground geological survey is carried out, the surface route geological profile is prepared, the surface geological basis is provided for the geophysical interpretation, the geological interpretation basis is reliable, the blindness is reduced, and the surface geological-underground wide area profile comprehensive map is prepared, that is, Figure 6 , 7 A, B, C and Figure 8 A, B, C of

[0069] S33: Combined with the regional geological map, the ground route geological survey, the interpretation marker layer and the interpretation model, the wide area inversion profile comprehensive geological interpretation is carried out.

[0070] The specific steps of step S33 are:

[0071] S331: The reliable marker layer and the obvious fault structure are interpreted first; combined with the ground route geological survey, the carbonate rock bottom boundary of the Qingxudong group, the top and bottom of the Wuxun group with large upper and lower electrical property change are interpreted first, and the fault with obvious dislocation can be interpreted first Figure 6 , Figure 7 , Figure 8 Marker layers 1, 2 and 3 and faults; if there is a neighboring two-dimensional seismic profile near the wide area profile, the wide area interpretation can be corrected according to the two-dimensional seismic, the overall trend of the stratum in the same tectonic background is mastered, and the stratum distribution trend of the corrected marker layer is mastered,Figure 3 The middle two-dimensional seismic provides basis for GY20-1 wide area stratum interpretation;

[0072] S332: The layer system with strong multi-solution needs to be combined with surface geology, regional stratum thickness and lithological characteristics to exclude multi-solution; for example Figure 8 The middle D position wide area profile shows high resistance, and needs to be combined with known conditions such as surface geology along the geophysical line, regional stratum thickness and thickness to repeatedly adjust and remove multi-interpretation; Figure 8 The middle F position wide area profile with more than 3000m has poor reliability;

[0073] S333: For the target layer and the combination with the same lithology of the upper and lower strata, it is difficult to distinguish Figure 6 and 7 D of Figure 8 E of, when doing geological horizon interpretation, only reasonable stratification position can be speculated through regional stratum thickness, and this method has the same principle as two-dimensional seismic in the case of non-obvious seismic wave impedance of geological stratification, two-dimensional seismic is also used to find a similar obvious phase axis to explain and then move downward or upward; for example Figure 8 The lower part of E Wutuan group shows low resistance, so the low resistance of Wutuan group is taken as a standard, and each stratum is reasonably divided according to the thickness of each stratum and the surface geological conditions.

[0074] S4: According to the depth and distribution characteristics of the interpreted geological profile of the target layer, combined with the structure preservation condition, surface drilling construction condition, and considering the drilling budget, the survey well position is deployed; based on Figure 8 According to the geological-wide area interpretation, Figure 9 The stratum and structure characteristics are clearly displayed to provide basis for drilling deployment and drilling depth prediction, according to the interpreted geological profile, combined with the structure preservation condition, surface drilling construction condition, and considering the drilling budget, the well position and alternative well position suggestions are proposed; and the depth and thickness of each stratum of the pre-drilling well are calculated through the wide area electromagnetic interpretation profile to prepare the pre-drilling columnar chart, which provides basis for the geological and engineering design of the survey well.

[0075] The above are only preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for well site deployment in a shale gas prospective area survey, characterized in that, The method comprises the following steps: S1: firstly, according to the target area of the prospective area geological survey evaluation, combining with the regional tectonic geological conditions, based on the cost-prospecting geological target effect method, a wide area electromagnetic profile is deployed; S2: collecting adjacent area or adjacent well logging or formation electromagnetic information, establishing electromagnetic-geological interpretation model, analyzing the electromagnetic difference of stratum lithology, and proposing interpretation marker bed; S3: combining with the geological background, adjacent geophysical lines, drilling data, forming a wide area electromagnetic method comprehensive geological interpretation method, removing the multi-solution, and interpreting the shale depth and distribution geological information of the target layer; S4: according to the interpretation geological profile of the target layer depth and distribution characteristics, combining with the tectonic preservation conditions, surface drilling construction conditions, and considering the drilling budget, the survey well location is deployed; The cost-prospecting geological target effect method comprises: S11: deploying geophysical lines vertically along the regional tectonic line; S12: starting from the outcrop point of the target layer to the deep buried area; S13: the geophysical line passes through the intended drilling target point selected by the geological survey; S14: the length of the geophysical line is controlled by the regional structure near the intended drilling target point; S15: according to the practice, the wide area electromagnetic profile is used to deploy drilling, the acquisition point and point spacing is 100m, the point spacing near the intended drilling target point is 20m, and the single point acquisition time is at least 4 hours; after ensuring the single point acquisition quality, the control of the regional tectonic unit, and the deployment of the geophysical line for the well, unnecessary geophysical lines are not deployed; The specific steps of the step S2 are: S21: resistivity test is conducted on different stratum rocks in the study area, the resistivity difference of different lithology is analyzed, and under the condition of no water, the resistivity of carbonate rock is higher than that of shale; S22: analyzing the resistivity logging curve of the adjacent well, the difference between the carbonate rock and the underlying shale is obvious, and the bottom boundary of the carbonate rock is the marker bed; S23: directly collecting single point MT resistivity curve at the well point position of the adjacent well; S24: according to the rock-electricity relationship curve, the marker bed is found out, and the interpretation model is established.

2. The method according to claim 1, wherein, In the step S1, through the shale gas basic geological survey and sampling of the prospective area, various shale gas drawings are prepared, and the drilling target area is screened according to the selection and evaluation procedure.

3. The method according to claim 1, wherein, The specific steps of the step S3 are: S31: based on the method provided by the wide area electromagnetic manufacturer, one-dimensional and two-dimensional inversion of the wide area profile is conducted, and the graph display is realized by using CAD software; S32: ground geological survey is conducted along the geophysical line, the surface route geological profile is prepared, the surface geological basis is provided for geophysical interpretation, and the surface geological-underground wide area profile comprehensive map is prepared; S33: combining with the regional geological map, ground route geological survey, interpretation marker bed, and interpretation model, the wide area inversion profile comprehensive geological interpretation is conducted.

4. The method according to claim 3, wherein, The specific steps of the step S33 are: S331: the reliable marker bed and obvious fault structure are interpreted first; combining with the ground route geological survey, the bottom boundary of the carbonate rock, the upper and lower electrical property change is large, the top and bottom are interpreted first, the fault with obvious dislocation is interpreted first; if there is adjacent two-dimensional seismic profile near the wide area profile, the wide area interpretation is corrected according to the two-dimensional seismic, the overall trend of the stratum in the same tectonic background is mastered, and the stratum distribution trend of the corrected marker bed is corrected. S332: The layer system with strong multi-solution needs to be combined with surface geology, regional stratum thickness and lithological characteristics to exclude multi-solution; S333: For the target layer and the combination of the upper and lower strata with consistent lithology, it is difficult to distinguish on the electromagnetic profile due to the consistent electrical characteristics, and only reasonable speculation of the layer position can be made through regional stratum thickness when doing geological horizon interpretation.

5. The method for well site deployment in a shale gas prospective area survey according to claim 1, characterized in that, The step S4 proposes well site and alternative well site suggestions according to the interpreted geological profile, combined with tectonic preservation conditions, surface drilling construction conditions and considering drilling budget; and calculates the burial depth and thickness of each stratum of the pre-drilling well through the wide-area electromagnetic interpretation profile, and prepares a pre-drilling columnar graph to provide a basis for survey well geology and engineering design.

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