A method for optimizing the location of exploration well boreholes

Abstract

This invention discloses a method for optimizing the location of exploration well boreholes, belonging to the field of offshore oil drilling technology. The method includes: determining a hazardous area and a first predetermined borehole location, wherein the hazardous area is determined based on hazardous factor information, and the first predetermined borehole location is an initial location determined according to a well location design table; determining the borehole location, based on the hazardous area and the first predetermined borehole location, determining whether the first predetermined borehole location is located within the hazardous area; if not, the borehole location corresponds to the first predetermined borehole location; if it is located within the hazardous area, moving the jack-up drilling platform so that the predetermined borehole location of the jack-up drilling platform is transferred from the first predetermined borehole location to a second predetermined borehole location corresponding to the location not located in the hazardous area, and the borehole location corresponds to the second predetermined borehole location. This invention allows the jack-up drilling platform and borehole location to avoid hazardous areas, enabling risk avoidance and location optimization in hazardous areas, thereby reducing drilling construction risks.

Description

Technical Field

[0001] This invention belongs to the field of offshore oil drilling technology, and particularly relates to a method for optimizing the location of exploration well boreholes. Background Technology

[0002] To determine the existence and boundaries of oil and gas reservoirs in offshore oil fields, industrial evaluation of these reservoirs is necessary. This requires drilling numerous exploration wells, primarily using jack-up platforms. Exploration well drilling operations involve conducting site surveys centered on the designed well locations, based on offshore geophysical survey results and reservoir design. These surveys include engineering geophysical investigations and engineering geological surveys. Engineering geophysical investigations reveal seabed topography and shallow geological features, while engineering geological surveys involve borehole sampling to obtain soil parameters and bearing capacity information.

[0003] The presence of hazardous geological features on the seabed, such as faults, ancient river channels, and shallow gas formations, as well as submarine infrastructure like pipelines and cables, poses a danger to drilling operations by exploration vessels. Currently, the conventional method for determining the location of exploration wells is based on a well location design table. However, without considering the aforementioned hazardous geological features and submarine infrastructure, risk analysis, risk avoidance, and optimal location selection are often conducted, easily leading to drilling risks. Incidents such as drill bit damage, mud loss during drilling, gas surges, and surface water surges have occurred during offshore operations, posing significant dangers to exploration vessels, sampling equipment, and personnel, and causing considerable economic losses.

[0004] With the advancement of the national "Seven-Year Action Plan," the number of offshore exploration wells drilled annually has reached over 500, and the number of backup sites requiring investigation has reached over 1,000 per year. The conventional methods for determining the location of exploration wells are clearly not in line with the requirements of exploration operation plans and the search for large oil reservoirs. To a certain extent, this reduces the possibility of discovering large oil reservoirs and also delays the oilfield development and exploitation process. Therefore, it is urgent to improve the conventional methods for determining the location of exploration wells. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art and aims to provide a method for optimizing the location of exploration well boreholes. This method allows jack-up drilling platforms and borehole locations to avoid dangerous areas, enabling risk avoidance and location optimization of dangerous areas, thereby reducing the risks of borehole construction.

[0006] To achieve the above objectives, the present invention provides a preferred method for the location of an exploration well borehole. A jack-up drilling platform has a bow leg below the bow and two stern legs below the stern. The predetermined borehole location is located on the stern side and between the two stern legs. The predetermined borehole location corresponds to at least one of a first predetermined borehole location and a second predetermined borehole location. The preferred method includes:

[0007] The danger zone and the first predetermined location of the borehole are determined. The danger zone is determined based on the danger factor information. The danger zone includes at least one of the following: shallow gas danger zone, fault danger zone, paleochannel danger zone, and submarine pipeline / cable danger zone. The danger factor information includes at least one of the following: shallow gas location information, fault location information, paleochannel location information, and submarine pipeline / cable location information. The first predetermined location of the borehole is the initial location determined according to the well location design table.

[0008] Determine the drilling location, and based on the danger zone and the first predetermined drilling location, determine whether the first predetermined drilling location is located within the danger zone.

[0009] If not located in a dangerous area, the drilling location corresponds to the first predetermined drilling position;

[0010] If located in a dangerous area, the jack-up drilling platform is moved so that the predetermined drilling position of the jack-up drilling platform is transferred from the first predetermined drilling position to the second predetermined drilling position corresponding to a location not in a dangerous area, so that the bow leg and stern leg are located in the same geological structure and do not cross the dangerous area between the bow leg and stern leg, and the drilling position corresponds to the second predetermined drilling position.

[0011] Furthermore, when determining the danger zone and the first predetermined location of the borehole, the shallow gas danger zone is the area where the top of the shallow gas layer is buried at a depth less than the borehole depth and the distance from the boundary of the shallow gas zone is less than the first safety distance L1, where L1 = A + B + C.

[0012] In the formula: A is the length of the jack-up drilling platform; B is the positioning radius; C is the safety distance;

[0013] If the first predetermined drilling position is located in the shallow gas hazard zone, the self-elevating drilling platform is moved to transfer its predetermined drilling position to a corresponding second predetermined drilling position, wherein the second predetermined drilling position is greater than or equal to the first safety distance L1 from the boundary of the shallow gas zone.

[0014] Furthermore, if the first predetermined location of the borehole is located in the shallow gas hazard zone, and if the shallow gas zone covers the entire investigation area or the jack-up drilling platform needs to be moved a distance exceeding the drilling range of the directional well, engineering measures shall be taken to release the shallow gas, and the borehole location shall correspond to the first predetermined location of the borehole.

[0015] Furthermore, when the self-elevating drilling platform is positioned with its bow facing the subsea pipeline cable in the first predetermined location of the drilling hole and the danger zone and the first predetermined location of the drilling hole, the danger zone of the subsea pipeline cable includes the area where the distance from the subsea pipeline cable is less than the second safety distance L2.

[0016] L2 = A + B + C1

[0017] In the formula: C1 is the safe distance for pipelines and cables.

[0018] If the first predetermined drilling position is located in the dangerous area of ​​the submarine pipeline and cable, the jack-up drilling platform is moved away from the submarine pipeline and cable to transfer its predetermined drilling position to a second predetermined drilling position, wherein the distance between the second predetermined drilling position and the submarine pipeline and cable is greater than or equal to the second safety distance.

[0019] If the distance between the first predetermined drilling location and the submarine pipeline / cable is greater than or equal to the second safety distance, the first predetermined drilling location is not located in the danger zone of the submarine pipeline / cable; or

[0020] When a jack-up drilling platform is positioned with its bow facing away from subsea pipelines and cables, the danger zone for the subsea pipelines and cables includes areas where the distance to the subsea pipelines and cables is less than the third safety distance L3.

[0021] L3 = B + C1

[0022] If the first predetermined drilling position is located in the danger zone of the submarine pipeline and cable, the jack-up drilling platform is moved away from the submarine pipeline and cable to transfer its predetermined drilling position to a position corresponding to the second predetermined drilling position, where the distance between the second predetermined drilling position and the submarine pipeline and cable is greater than or equal to the third safety distance.

[0023] If the distance between the first predetermined drilling location and the submarine pipeline / cable is greater than or equal to the third safety distance, the first predetermined drilling location is not located in the danger zone of the submarine pipeline / cable.

[0024] Furthermore, when determining the danger zone and the first predetermined location of the borehole, the fault danger zone includes the area located on the hanging wall of a normal fault, the area located on the footwall of a normal fault and at a distance less than the fourth safety distance L4 from the fault line, the area located on the hanging wall of a reverse fault, and the area located on the footwall of a reverse fault and at a distance less than the fourth safety distance L4 from the fault line.

[0025] L4 = A + B + C

[0026] If the first predetermined drilling position is located in the fault danger zone, the self-elevating drilling platform is moved to transfer its predetermined drilling position to the corresponding second predetermined drilling position, which is located on the footwall and at a distance greater than or equal to the fourth safety distance L4 from the fault line.

[0027] Furthermore, in determining the danger zone and the first predetermined drilling location, where the first predetermined drilling location is located outside the ancient river channel, and the jack-up drilling platform is positioned with its bow facing the ancient river channel boundary line, the ancient river channel danger zone includes areas where the ancient river channel burial depth is less than the drilling depth and the distance from the ancient river channel boundary line is less than the fifth safety distance L5.

[0028] L5 = A + B + C

[0029] If the first predetermined drilling position is located in the dangerous area of ​​the ancient river channel, the self-elevating drilling platform is moved away from the boundary of the ancient river channel and in the opposite direction to the positioning bow, so that its predetermined drilling position is transferred to the corresponding second predetermined drilling position, the distance between the second predetermined drilling position and the boundary line of the ancient river channel is greater than or equal to the fifth safety distance L5.

[0030] When the first predetermined drilling location is outside the ancient river channel, and the jack-up drilling platform is positioned with its bow facing away from the ancient river channel boundary, the ancient river channel danger zone includes areas where the ancient river channel burial depth is less than the drilling depth and the distance from the ancient river channel boundary is less than the sixth safety distance L6.

[0031] L6 = B + C

[0032] If the first predetermined drilling position is located in the dangerous area of ​​the ancient river channel, the self-elevating drilling platform is moved away from the boundary of the ancient river channel and in the opposite direction to the positioning bow, so that its predetermined drilling position is transferred to the corresponding second predetermined drilling position, the distance between the second predetermined drilling position and the boundary line of the ancient river channel is greater than or equal to the sixth safety distance L6.

[0033] The first predetermined drilling location is within the ancient riverbed. The dangerous area of ​​the ancient riverbed includes areas where the ancient riverbed depth is less than the drilling depth and the distance from the ancient riverbed boundary line is less than the fifth safety distance L5.

[0034] If the first predetermined drilling position is located in the dangerous area of ​​the ancient river channel, the jack-up drilling platform will be moved away from the ancient river channel boundary or towards the center of the ancient river channel, so that its predetermined drilling position is transferred to the corresponding second predetermined drilling position. The distance between the second predetermined drilling position and the ancient river channel boundary line is greater than or equal to the fifth safety distance L5.

[0035] If the first predetermined location of the borehole is located within the ancient river channel and is greater than or equal to the fifth safety distance L5 from the boundary of the ancient river channel, then the first predetermined location of the borehole is not located in the dangerous area of ​​the ancient river channel.

[0036] If the burial depth of the ancient riverbed corresponding to the first predetermined location of the borehole is greater than the borehole depth, the first predetermined location of the borehole is not located in the dangerous area of ​​the ancient riverbed.

[0037] Furthermore, the offshore exploration well drilling location corresponding to the predetermined drilling location also includes a third predetermined drilling location. After determining the drilling location, the following is also included:

[0038] The third predetermined drilling position is determined. According to the engineering geophysical survey report, if the horizontal soil composition characteristics of the strata at the bow leg position and the stern leg position, which are located within or outside the ancient river channel, differ significantly, the jack-up drilling platform is moved to transfer the predetermined drilling position to the corresponding third predetermined drilling position. The third predetermined drilling position is not located in a danger zone, and the bow leg and stern leg are located in the same geological structure, and the bow leg and stern leg do not cross the danger zone.

[0039] Furthermore, when determining whether the first predetermined location of the borehole is located in a hazardous area, the hazardous area shall be determined in the following order:

[0040] Determine whether the first predetermined location of the borehole is located in a shallow gas hazard zone;

[0041] Determine whether the first predetermined location of the borehole is located in a fault hazard zone and / or an ancient river channel hazard zone and / or a submarine pipeline / cable hazard zone.

[0042] Furthermore, the offshore exploration well drilling position corresponding to the predetermined drilling position also includes the fourth predetermined drilling position determined by the requirements of reservoir exploration and development and the design trajectory requirements of directional wells. If it is located in a dangerous area, the displacement distance of the predetermined drilling position of the jack-up drilling platform from the first predetermined drilling position to the fourth predetermined drilling position is less than the distance moved from the first predetermined drilling position to the second predetermined drilling position. The drilling position corresponds to the fourth predetermined drilling position.

[0043] The embodiments of the present invention provide a method for optimizing the location of exploration wells. Before drilling operations in offshore oilfields, the method can take into account hazardous geological features such as faults, paleochannels, and shallow gas, as well as submarine facilities such as submarine pipelines and cables. It can optimize the location of the bow and stern legs of the jack-up drilling platform to avoid risks. This method can reduce the risks of drilling and pile driving, improve sampling quality, enhance the safety of the jack-up platform in exploration well placement and drilling operations, and promote offshore oilfield development. Attached Figure Description

[0044] Figure 1 This is a structural schematic diagram of a jack-up drilling platform for a preferred method of drilling location for exploration wells provided in an embodiment of the present invention;

[0045] Figure 2 This is a flowchart of a preferred method for determining the drilling location of an exploration well, provided by an embodiment of the present invention;

[0046] Figure 3This is a distribution map of shallow gas zones and fault lines provided in an embodiment of the present invention;

[0047] Figure 4 This is a distribution map of fault lines and ancient river channels provided in an embodiment of the present invention;

[0048] Figure 5 This is a distribution map of ancient river channels provided in an embodiment of the present invention;

[0049] Figure 6 This is a distribution map of shallow gas zones, fault lines, and paleochannels provided in an embodiment of the present invention;

[0050] Figure 7 This is a distribution map of shallow gas zones, fault lines, and paleochannels provided in an embodiment of the present invention;

[0051] Figure 8 This is a distribution map of shallow gas zones and fault lines provided in an embodiment of the present invention;

[0052] Figure 9 This is a distribution diagram of submarine pipelines and cables provided in an embodiment of the present invention.

[0053] Among them: 1. Jack-up drilling platform; 11. Bow leg; 12. Tail leg; 13. Drilling hole predetermined position; 2. First predetermined drilling hole position; 3. Second predetermined drilling hole position; 4. Shallow gas zone; 5. Fault line; 6. Ancient river channel; 7. Submarine pipeline and cable. Detailed Implementation

[0054] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0055] Embodiments of the present invention provide a preferred method for the location of exploration well boreholes, such as... Figure 1 , Figure 2 As shown, the jack-up drilling platform 1 has a bow leg 11 below the bow and a stern leg 12 on each side below the stern. The predetermined drilling position 13 is located on the stern side and between the two stern legs 12. Before drilling operations are carried out at the predetermined position, the jack-up drilling platform 1 needs to drill a hole to analyze the soil conditions and bearing capacity of the location, providing foundation support for the jack-up drilling platform's placement and drilling operations. The predetermined drilling position 13 corresponds to at least one of a first predetermined drilling position 2 and a second predetermined drilling position 3. Preferred methods include:

[0056] Step S1: Determine the danger zone and the first predetermined location 2 of the borehole. The danger zone is determined based on the danger factor information. The danger zone includes at least one of the following: shallow gas danger zone, fault danger zone, paleochannel danger zone, and submarine pipeline / cable danger zone. The danger factor information includes at least one of the following: shallow gas location information, fault location information, paleochannel location information, and submarine pipeline / cable location information. The first predetermined location 2 of the borehole is the initial location determined according to the well location design table.

[0057] Step S2: Determine the drilling location. Based on the danger zone and the first predetermined drilling location 2, determine whether the first predetermined drilling location 2 is located within the danger zone.

[0058] Step S3: If not located in a dangerous area, the drilling position corresponds to the first predetermined drilling position 2.

[0059] Step S4: If located in a dangerous area, move the jack-up drilling platform 1 so that the predetermined drilling position 13 of the jack-up drilling platform 1 is transferred from the first predetermined drilling position 2 to the second predetermined drilling position 3 corresponding to a drilling position not located in a dangerous area, so that the bow leg 11 and the stern leg 12 are located in the same geological structure and do not cross the dangerous area between the bow leg 11 and the stern leg 12, and the drilling position corresponds to the second predetermined drilling position 3.

[0060] Information on fault location, paleochannel location, shallow gas location, and submarine pipeline / cable location can all be obtained from the geological feature map in the engineering geophysical survey report. Drilling at the first predetermined location 2 or the second predetermined location 3, which is not located in a dangerous area, ensures that the bow leg 11 or stern leg 12 is located in the same geological structure. The same geological structure means that the bow leg 11 or stern leg 12 is located in the same geological structure as a whole, such as not crossing the fault plane, being located in the upper or lower layer, and both the bow leg 11 and stern leg 12 are located in the same geological structure, such as being located within or outside the paleochannel 6. The bow leg 11 and stern leg 12 do not cross a dangerous area, meaning there is no dangerous area between the bow leg 11 and stern leg 12, such as the jack-up drilling platform 1 not being erected on the fault line 5. By using this preferred method, the positions of the bow leg 11 and the stern leg 12 of the self-elevating drilling platform 1 can be avoided by combining the dangerous area and the first predetermined position 2 of the borehole, and the position of the borehole can be optimized to reduce the drilling construction risk and improve the sampling quality.

[0061] Example 1: As Figure 3As shown, the present invention provides a preferred method for determining the location of an exploration well borehole. The preferred method includes: determining a hazardous area and a first predetermined location 2 for the borehole. The hazardous area is determined based on hazardous factor information. The hazardous area includes at least one of shallow gas hazardous area, fault hazardous area, paleochannel hazardous area, and submarine pipeline / cable hazardous area. The hazardous factor information includes at least one of shallow gas location information, fault location information, paleochannel location information, and submarine pipeline / cable location information. The first predetermined location 2 for the borehole is an initial location determined according to a well location design table. Determine the borehole predetermined position 13. Based on the danger zone and the first predetermined borehole position 2, determine whether the first predetermined borehole position 2 is located within the danger zone: if it is not located within the danger zone, the borehole predetermined position 13 corresponds to the first predetermined borehole position 2; if it is located within the danger zone, move the jack-up drilling platform 1 so that the borehole predetermined position 13 of the jack-up drilling platform 1 is transferred from the first predetermined borehole position 2 to the second predetermined borehole position 3 corresponding to the borehole not located within the danger zone, so that the bow leg 11 and the stern leg 12 are located in the same geological structure and do not cross the danger zone between the bow leg 11 and the stern leg 12.

[0062] When determining the danger zone and the first predetermined location 2 of the borehole, the shallow gas danger zone is the area where the top of the shallow gas layer is less than the borehole depth and the distance from the boundary of the shallow gas zone 4 is less than the first safety distance L1.

[0063] L1 = A + B + C

[0064] In the formula: A is the length of the jack-up drilling platform, which can be found in Chapter 1, Section 4 of the "Marine Drilling Handbook"; B is the positioning radius, which can be found in Chapter 1, Section 4 of the "Marine Drilling Handbook"; C is the safety distance, which can be found in Section 6 of the "Design Specification for Positioning of Jack-up Drilling Platforms".

[0065] If the first predetermined drilling position 2 is located in a shallow gas hazard zone, the self-elevating drilling platform 1 is moved so that its predetermined drilling position 13 is transferred to the corresponding second predetermined drilling position 3, and the distance between the second predetermined drilling position 3 and the boundary of the shallow gas zone 4 is greater than or equal to the first safety distance L1.

[0066] If the first predetermined drilling position 2 is not located in the shallow gas hazard area, that is, the shallow gas top burial depth corresponding to the first predetermined drilling position 2 is greater than the drilling depth, or the shallow gas top burial depth is less than the drilling depth but the first predetermined drilling position 2 is more than the first safe distance L1 from the boundary of the shallow gas area 4, the predetermined drilling position 13 corresponds to the first predetermined drilling position 2.

[0067] In accordance with the requirements of the offshore well site survey specifications, the drilling depth is 40 meters. Preferably, the length A of the jack-up drilling platform 1 is 70 meters, the positioning radius B is 30 meters, the safety distance C is 20 meters, and the first safety distance L1 is 120 meters. This ensures that the bow leg 11, stern leg 12, and the predetermined drilling position 13 are all located outside the boundary of the shallow gas zone 4, guaranteeing the safety of drilling and pile driving operations, and improving the safety of the jack-up platform in exploration well positioning and drilling operations.

[0068] Furthermore, if the first predetermined drilling position 2 is located in a shallow gas hazard zone, and if the shallow gas zone 4 covers the entire survey area or the jack-up drilling platform 1 needs to be moved beyond the drilling range of the directional well, making it inconvenient to move the jack-up drilling platform 1 to the corresponding second predetermined drilling position 3, engineering measures will be taken to release the shallow gas. Drilling will then proceed after the shallow gas volume stabilizes, with the drilling position corresponding to the first predetermined drilling position 2. Here, "stable shallow gas volume" means that there are no horizontal bubbles or the amount of horizontal bubbles is small; engineering measures include drilling with a roller cone bit.

[0069] Example 2: Figure 9 As shown, the present invention provides a preferred method for determining the location of an exploration well borehole. The difference from Embodiment 1 is that, in determining the danger zone and the first predetermined location 2 of the borehole, when the self-elevating drilling platform 1 is positioned with its bow facing the submarine pipeline cable 7, the danger zone of the submarine pipeline cable includes the area where the distance from the submarine pipeline cable 7 is less than the second safety distance L2.

[0070] L2 = A + B + C1

[0071] In the formula: C1 is the safety distance for pipelines and cables, which can be found in Section 6 of the "Design Specification for Positioning of Self-elevating Drilling Platforms".

[0072] If the first predetermined drilling position 2 is located in a dangerous area of ​​the submarine pipeline and cable 7, the self-elevating drilling platform is moved away from the submarine pipeline and cable 7, so that its predetermined drilling position 13 is transferred to the corresponding second predetermined drilling position 3, and the distance between the second predetermined drilling position 3 and the submarine pipeline and cable 7 is greater than or equal to the second safety distance L2.

[0073] If the distance between the first predetermined drilling location 2 and the submarine pipeline / cable 7 is greater than or equal to the second safety distance L2, the first predetermined drilling location 2 is not located in the danger zone of the submarine pipeline / cable; or

[0074] When the jack-up drilling platform 1 is positioned with its bow facing away from the subsea pipeline cable 7, the danger zone for the subsea pipeline cable includes the area where the distance to the subsea pipeline cable 7 is less than the third safety distance L3.

[0075] L3 = B + C1

[0076] If the first predetermined drilling position 2 is located in the dangerous area of ​​the submarine pipeline and cable 7, the self-elevating drilling platform 1 is moved away from the submarine pipeline and cable 7, so that its predetermined drilling position 13 is transferred to the corresponding second predetermined drilling position 3, and the distance between the second predetermined drilling position and the submarine pipeline and cable 7 is greater than or equal to the third safety distance L3.

[0077] If the distance between the first predetermined drilling position 2 and the submarine pipeline / cable is greater than or equal to the third safety distance L3, the first predetermined drilling position 2 is not located in the danger zone of the submarine pipeline / cable.

[0078] The orientation of the jack-up platform is determined by the mainstream direction of the block where the exploration well is located and the winter and summer wind directions. The direction away from the pipeline and cable is the reverse extension of the perpendicular line from the first predetermined position 2 of the borehole to the submarine pipeline and cable 7. Preferably, the length A of the jack-up drilling platform 1 is 70 meters, the positioning radius B is 30 meters, the safety distance C1 for the pipeline and cable is 80 meters, the second safety distance L2 is 180 meters, and the third safety distance L3 is 110 meters. This ensures that when the jack-up drilling platform 1 is facing or away from the submarine pipeline and cable 7, after the jack-up drilling platform 1 is driven into the pile, the bow leg 11 or stern leg 12 closest to the submarine pipeline and cable 7 is far away from the submarine pipeline and cable 7. This ensures that the bow leg 11, stern leg 12, and the predetermined position 13 of the borehole are all far away from the submarine pipeline and cable 7, guaranteeing the safety of the submarine pipeline and cable facilities and the jack-up drilling platform 1.

[0079] Example 3: Figure 3 , Figure 4 , Figures 6 to 8 As shown, the present invention provides a preferred method for determining the location of exploration well boreholes. The difference from Embodiment 1 is that, when determining the danger zone and the first predetermined location 2 of the borehole, the fault danger zone includes areas located on the hanging wall of a normal fault, areas located on the footwall of a normal fault and whose distance from the fault line 5 is less than the fourth safety distance L4, areas located on the hanging wall of a reverse fault, and areas located on the footwall of a reverse fault and whose distance from the fault line 5 is less than the fourth safety distance L4.

[0080] L4 = A + B + C

[0081] If the first predetermined drilling position 2 is located in a fault danger zone, move the self-elevating drilling platform 1 so that its predetermined drilling position 13 is transferred to the corresponding second predetermined drilling position 3. The second predetermined drilling position 3 is located on the footwall and the distance from the fault line 5 is greater than or equal to the fourth safety distance L4.

[0082] Faults are classified into two main categories: normal faults and reverse faults. In normal faults, the hanging wall subsides relatively while the footwall rises relatively; in reverse faults, the hanging wall rises relatively while the footwall subsides relatively. When identifying fault hazard zones, the fault type can be determined based on the engineering geophysical survey report. The borehole location is then determined based on the fault type and its location on the hanging wall or footwall. A second predetermined location on the footwall, at a distance greater than or equal to the fourth safety distance L4 from the fault line, ensures that the borehole is located on a stable surface when the fault plane's dip angle is difficult to determine. This ensures that the sampling process does not traverse the fault plane, the sampled soil is free of fault fissures, and the soil quality is continuous and stable, thus improving sampling quality. Preferably, the length A of the jack-up drilling platform 1 is 70 meters, the positioning radius B is 30 meters, the safety distance C is 20 meters, and the fourth safety distance L4 is 120 meters. This ensures that the bow leg 11 or tail leg 12 does not penetrate the fault plane and is located in the lower layer, thus ensuring the safety of drilling and pile driving operations, obtaining reasonable soil data, and improving the safety of the jack-up platform in exploration well positioning and drilling operations.

[0083] Example 4: Figure 4 , Figure 5 As shown, the present invention provides a preferred method for determining the location of an exploration well borehole. The difference from Embodiment 1 is that, in determining the danger zone and the first predetermined borehole location 2, the first predetermined borehole location 2 is located outside the ancient river channel 6. When the jack-up drilling platform 1 is positioned with its bow facing the boundary line of the ancient river channel 6, the ancient river channel danger zone includes areas where the burial depth of the ancient river channel 6 is less than the borehole depth and the distance from the boundary line of the ancient river channel 6 is less than the fifth safety distance L5.

[0084] L5 = A + B + C

[0085] If the first predetermined drilling position 2 is located in the dangerous area of ​​the ancient river channel, the self-elevating drilling platform 1 is moved away from the boundary of the ancient river channel 6 and in the opposite direction to the positioning bow, so that its predetermined drilling position 13 is transferred to the corresponding second predetermined drilling position 3, and the distance between the second predetermined drilling position 3 and the boundary line of the ancient river channel 6 is greater than or equal to the fifth safety distance L5.

[0086] The first predetermined drilling location 2 is located outside the ancient river channel 6. When the jack-up drilling platform 1 is positioned with its bow facing away from the boundary line of the ancient river channel 6, the dangerous area of ​​the ancient river channel includes the area where the burial depth of the ancient river channel 6 is less than the drilling depth and the distance from the boundary line of the ancient river channel 6 is less than the sixth safety distance L6.

[0087] L6 = B + C

[0088] If the first predetermined drilling position 2 is located in the dangerous area of ​​the ancient river channel, the self-elevating drilling platform 1 is moved away from the boundary of the ancient river channel 6 and in the opposite direction to the positioning bow, so that its predetermined drilling position 13 is transferred to the corresponding second predetermined drilling position 3, and the distance between the second predetermined drilling position 3 and the boundary line of the ancient river channel 6 is greater than or equal to the sixth safety distance L6.

[0089] The first predetermined drilling location 2 is located within the ancient river channel 6. The dangerous area of ​​the ancient river channel includes the area where the burial depth of the ancient river channel 6 is less than the drilling depth and the distance from the boundary line of the ancient river channel 6 is less than the fifth safety distance L5.

[0090] If the first predetermined drilling position 2 is located in a dangerous area of ​​the ancient river channel 6, and the area of ​​the ancient river channel 6 is small, the jack-up drilling platform 1 will be moved away from the boundary of the ancient river channel 6; if the area of ​​the ancient river channel 6 is large, the jack-up drilling platform 1 will be moved towards the center of the ancient river channel 6, and its predetermined drilling position 13 will be transferred to the corresponding second predetermined drilling position 3. The distance between the second predetermined drilling position 3 and the boundary line of the ancient river channel 6 is greater than or equal to the fifth safety distance L5.

[0091] If the first predetermined location 2 of the borehole is located within the ancient river channel 6 and is greater than or equal to the fifth safety distance L5 from the boundary of the ancient river channel 6, then the first predetermined location 2 of the borehole is not located in the dangerous area of ​​the ancient river channel.

[0092] If the depth of the ancient river channel 6 corresponding to the first predetermined location 2 of the borehole is greater than the borehole depth, the first predetermined location 2 of the borehole is not located in the dangerous area of ​​the ancient river channel.

[0093] Preferably, the length A of the jack-up drilling platform 1 is 70 meters, the positioning radius B is 30 meters, the safety distance C is 20 meters, the fifth safety distance L5 is 120 meters, and the sixth safety distance L6 is 50 meters. This ensures that the bow leg 11 or the stern leg 12 are located outside the boundary line of the ancient river channel 6, which can reduce the differences in the characteristics of the soil composition in the horizontal direction, improve the sampling quality, ensure the safety of drilling and pile driving operations, and improve the safety of the jack-up platform in exploration well positioning and drilling operations.

[0094] Furthermore, the borehole location corresponding to borehole predetermined location 13 also includes a third predetermined borehole location, which, after determining the borehole location, also includes:

[0095] The third predetermined location for the borehole is determined. According to the engineering geophysical survey report, if the horizontal soil composition characteristics of the strata at the bow leg 11 location and the stern leg location are significantly different, whether located within or outside the ancient river channel 6, the jack-up drilling platform 1 is moved so that the predetermined borehole location 13 of the jack-up drilling platform 1 is transferred to the corresponding third predetermined location for the borehole. The third predetermined location for the borehole is not located in a dangerous area, and the bow leg 11 and the stern leg 12 are located in the same geological structure and do not cross a dangerous area between the bow leg 11 and the stern leg 12.

[0096] If the horizontal soil composition characteristics at the bow leg 11 and stern leg positions differ significantly, it will affect the accuracy of sampling. By setting an additional third predetermined position, the sampling quality can be improved. For example, if the bow leg 11 of the self-elevating drilling platform 1 consists of clay (0 to below the mud surface to -2.5 meters), silt (-2.5 to -4 meters), and sand (-4 to -7 meters) from top to bottom, and the stern leg position consists of silt (0 to -1.0), clay (-1.0 to -4.5), and sand (-4.5 to -7 meters) from top to bottom, the difference in composition order and thickness of each component will reduce the accuracy of sampling.

[0097] Example 5: Figure 7 As shown, the present invention provides a preferred method for determining the location of an exploration well borehole. When determining whether the first predetermined location 2 of the borehole is located in a dangerous area, if the predetermined location 13 of the borehole simultaneously has two or more influencing factors, including faults, paleochannels 6, shallow gas, and pipelines and cables, the dangerous area is determined in the following order:

[0098] Step 1: Determine whether the first predetermined location 2 of the borehole is located in a shallow gas hazard zone;

[0099] Step 2: Determine whether the first predetermined location 2 of the borehole is located in a fault danger zone and / or an ancient river channel danger zone and / or a submarine pipeline and cable danger zone.

[0100] Since shallow gas zone 4 is a high-risk factor affecting the positioning of the self-elevating drilling platform 1 and drilling operations, when selecting the drilling location, it is necessary to prioritize avoiding the shallow gas danger zone and determine its displacement distance; then avoid fault danger zone, ancient river channel danger zone, and submarine pipeline and cable danger zone, and determine their displacement distances respectively. The final determined location is the reasonable drilling location.

[0101] Example 6: The present invention provides a preferred method for determining the drilling location of an exploration well. The difference from Example 5 is that the drilling location of the offshore exploration well corresponding to the predetermined drilling location 13 also includes a fourth predetermined drilling location determined by the requirements of reservoir exploration and development and the design trajectory requirements of directional wells. If it is located in a dangerous area, the displacement distance of the predetermined drilling location 13 of the jack-up drilling platform 1 from the first predetermined drilling location 2 to the fourth predetermined drilling location is less than the distance moved from the first predetermined drilling location 2 to the second predetermined drilling location 3. The drilling location corresponds to the fourth predetermined drilling location.

[0102] The requirements for reservoir exploration and development refer to the ability of the selected borehole location to identify the reservoir trap, oil layer depth and thickness, and to conduct reserve evaluation. The requirements for directional well design trajectory refer to the ability of the selected borehole location to reach the trap depth through directional trajectories and other measures, and to encounter the oil layer and obtain oil and gas shows. In this embodiment, since both the requirements for reservoir exploration and development and the requirements for directional well design trajectory are taken into account, if the displacement distance determined according to the requirements for reservoir exploration and development and the requirements for directional well design trajectory is less than the displacement distance determined according to the above embodiments, the displacement distance determined according to the requirements for reservoir exploration and development and the requirements for directional well design trajectory can be used for displacement, and is not limited to the displacement distances of embodiments 1 to 5.

[0103] Example 7: Figure 7 As shown in the figure, in a specific embodiment of the preferred method for determining the location of an exploration well according to the present invention, the well location design coordinates of an exploration well in the Bohai Oilfield are: X = 4295484.97mN, Y = 411610.99mE. According to the engineering geophysical survey report, there are three hazardous geological features within the well site area: fault, buried ancient river channel 6, and shallow gas.

[0104] According to the engineering geophysical survey report, the center of the first predetermined location 2 of the borehole is located within the shallow gas area, and the center of the first predetermined location 2 of the borehole is also located within the ancient river channel 6. In addition, there is a fault located exactly at the boundary of the shallow gas. The top of the shallow gas is buried at a depth of 3-5 meters, and the center of the first predetermined location 2 of the borehole is 290 meters away from the boundary of the shallow gas.

[0105] Since the center of borehole at the first predetermined location 2 is within the shallow gas zone A1, it needs to be moved towards the nearest boundary point of the shallow gas. The moving angle is 16.6 degrees due south east, ensuring a distance of more than 120 meters and at least 406 meters.

[0106] According to the engineering geophysical survey report, the fault is a reverse fault. The north side of fault line F2 is the hanging wall and the south side is the footwall. The location selected after passing through the shallow gas hazard area is exactly in the footwall of the reverse fault, and the distance to fault line 5 of fault F2 is 105 meters. It belongs to a stable stratum and meets the requirements.

[0107] After passing through the shallow gas hazard zone and the fault hazard zone, the selected location is 165 meters from the boundary line of the left ancient river channel 6, which is more than 120 meters away from the boundary line of the ancient river channel 6. This location is the second predetermined location 3 for drilling.

[0108] Due to the difficulty of directional well design, the actual relocation distance was 399 meters. The coordinates of the well center after relocation are: X = 4295102.00mN, Y = 411725.00mE.

[0109] Example 8: As Figure 8 , Figure 9As shown in the figure, in a specific embodiment of the preferred method for determining the location of an exploration well according to the present invention, the well location design coordinates of an exploration well in the Bohai Oilfield are: X = 4228599.03mN, Y = 475837.24mE. According to the engineering geophysical survey report, there are faults, shallow gas areas, and submarine pipelines / cables within the well site area.

[0110] According to the engineering geophysical survey report, the first predetermined location 2 of the borehole is more than 120 meters away from the boundary of the shallow gas zone 4 and the fault line 5, which meets the requirements of the first safety distance L1 and the fourth safety distance L4.

[0111] Given the seabed current velocity and direction at this well location, and the jack-up platform's heading being 230° directly towards the pipeline, the distance between the center of the first predetermined drilling position 2 and the nearest subsea pipeline cable 7 is 89 meters, which does not meet the distance requirement of the second safety distance L2. After relocation, the distance from the predetermined drilling position 13 to the subsea pipeline cable 7 needs to be greater than or equal to 180 meters.

[0112] The self-elevating drilling platform 1 can be moved 100 meters away from the pipeline by moving it away from the submarine pipeline cable 7. Combined with the reservoir and directional well design, it can be moved 189 meters away from the pipeline. The coordinates of the well center after the relocation are: X = 4228663.03mN, Y = 475913.24mE.

[0113] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A preferred method for determining the location of an exploration well borehole, wherein a jack-up drilling platform has a bow leg below the bow and a stern leg on each side below the stern, and the predetermined borehole location is located on the stern side and between the two stern legs, characterized in that... The predetermined drilling location corresponding to the offshore exploration well drilling location includes at least one of a first predetermined drilling location and a second predetermined drilling location, and the preferred method includes: The danger zone and the first predetermined location of the borehole are determined. The danger zone is determined based on the danger factor information. The danger zone includes at least one of the following: shallow gas danger zone, fault danger zone, paleochannel danger zone, and submarine pipeline / cable danger zone. The danger factor information includes at least one of the following: shallow gas location information, fault location information, paleochannel location information, and submarine pipeline / cable location information. The first predetermined location of the borehole is the initial location determined according to the well location design table. Determine the drilling location, and based on the danger zone and the first predetermined drilling location, determine whether the first predetermined drilling location is located within the danger zone. If not located in a dangerous area, the drilling location corresponds to the first predetermined drilling position; If located in a dangerous area, move the jack-up drilling platform so that the predetermined drilling position of the jack-up drilling platform is transferred from the first predetermined drilling position to the second predetermined drilling position corresponding to a location not in a dangerous area, so that the bow leg and stern leg are located in the same geological structure and do not cross the dangerous area between the bow leg and stern leg, and the drilling position corresponds to the second predetermined drilling position. Specifically, when determining the danger zone and the first predetermined location of the borehole, the shallow gas danger zone is the area where the top of the shallow gas layer is less than the borehole depth and the distance from the boundary of the shallow gas zone is less than the first safety distance L1. L1 = A + B + C In the formula: A is the length of the jack-up drilling platform; B is the positioning radius; C is the safety distance; If the first predetermined drilling position is located in the shallow gas hazard zone, the self-elevating drilling platform is moved to transfer its predetermined drilling position to a corresponding second predetermined drilling position, wherein the second predetermined drilling position is greater than or equal to the first safety distance L1 from the boundary of the shallow gas zone.

2. The preferred method for determining the drilling location of an exploration well as described in claim 1, characterized in that, If the first predetermined drilling position is located in the shallow gas hazard zone, and if the shallow gas zone covers the entire survey area or the jack-up drilling platform needs to be moved beyond the drilling range of the directional well, engineering measures will be taken to release the shallow gas, and the drilling position will correspond to the first predetermined drilling position.

3. The preferred method for determining the drilling location of an exploration well as described in claim 1, characterized in that, When the self-elevating drilling platform is positioned with its bow facing the subsea pipeline cable in the first predetermined location of the drilling hole and the danger zone of the subsea pipeline cable is determined, the danger zone of the subsea pipeline cable includes the area where the distance from the subsea pipeline cable is less than the second safety distance L2. L2 = A + B + C1 In the formula: C1 is the safe distance for pipelines and cables. If the first predetermined drilling position is located in the dangerous area of ​​the submarine pipeline and cable, the jack-up drilling platform is moved away from the submarine pipeline and cable to transfer its predetermined drilling position to a second predetermined drilling position, wherein the distance between the second predetermined drilling position and the submarine pipeline and cable is greater than or equal to the second safety distance. If the distance between the first predetermined drilling location and the submarine pipeline / cable is greater than or equal to the second safety distance, the first predetermined drilling location is not located in the danger zone of the submarine pipeline / cable. or When a jack-up drilling platform is positioned with its bow facing away from subsea pipelines and cables, the danger zone for the subsea pipelines and cables includes areas where the distance to the subsea pipelines and cables is less than the third safety distance L3. L3 = B + C1 If the first predetermined drilling position is located in the danger zone of the submarine pipeline and cable, the jack-up drilling platform is moved away from the submarine pipeline and cable to transfer its predetermined drilling position to a position corresponding to the second predetermined drilling position, where the distance between the second predetermined drilling position and the submarine pipeline and cable is greater than or equal to the third safety distance. If the distance between the first predetermined drilling location and the submarine pipeline / cable is greater than or equal to the third safety distance, the first predetermined drilling location is not located in the danger zone of the submarine pipeline / cable.

4. The preferred method for determining the drilling location of an exploration well as described in claim 1, characterized in that, When determining the danger zone and the first predetermined location of the borehole, the fault danger zone includes the hanging wall of a normal fault, the footwall of a normal fault and the distance from the fault line less than the fourth safety distance L4, the hanging wall of a reverse fault, and the footwall of a reverse fault and the distance from the fault line less than the fourth safety distance L4. L4 = A + B + C If the first predetermined drilling position is located in the fault danger zone, the self-elevating drilling platform is moved to transfer its predetermined drilling position to the corresponding second predetermined drilling position, which is located on the footwall and at a distance greater than or equal to the fourth safety distance L4 from the fault line.

5. The preferred method for determining the drilling location of an exploration well as described in claim 1, characterized in that, In determining the danger zone and the first predetermined drilling location, where the first predetermined drilling location is located outside the ancient river channel, and the jack-up drilling platform is positioned with its bow facing the ancient river channel boundary line, the ancient river channel danger zone includes areas where the ancient river channel burial depth is less than the drilling depth and the distance from the ancient river channel boundary line is less than the fifth safety distance L5. L5 = A + B + C If the first predetermined drilling position is located in the dangerous area of ​​the ancient river channel, the self-elevating drilling platform is moved away from the boundary of the ancient river channel and in the opposite direction to the positioning bow, so that its predetermined drilling position is transferred to the corresponding second predetermined drilling position, the distance between the second predetermined drilling position and the boundary line of the ancient river channel is greater than or equal to the fifth safety distance L5. When the first predetermined drilling location is outside the ancient river channel, and the jack-up drilling platform is positioned with its bow facing away from the ancient river channel boundary, the ancient river channel danger zone includes areas where the ancient river channel burial depth is less than the drilling depth and the distance from the ancient river channel boundary is less than the sixth safety distance L6. L6 = B + C If the first predetermined drilling position is located in the dangerous area of ​​the ancient river channel, the self-elevating drilling platform is moved away from the boundary of the ancient river channel and in the opposite direction to the positioning bow, so that its predetermined drilling position is transferred to the corresponding second predetermined drilling position, the distance between the second predetermined drilling position and the boundary line of the ancient river channel is greater than or equal to the sixth safety distance L6. The first predetermined drilling location is within the ancient riverbed. The dangerous area of ​​the ancient riverbed includes areas where the ancient riverbed depth is less than the drilling depth and the distance from the ancient riverbed boundary line is less than the fifth safety distance L5. If the first predetermined drilling position is located in the dangerous area of ​​the ancient river channel, the jack-up drilling platform will be moved away from the ancient river channel boundary or towards the center of the ancient river channel, so that its predetermined drilling position is transferred to the corresponding second predetermined drilling position. The distance between the second predetermined drilling position and the ancient river channel boundary line is greater than or equal to the fifth safety distance L5. If the first predetermined location of the borehole is located within the ancient river channel and is greater than or equal to the fifth safety distance L5 from the boundary of the ancient river channel, then the first predetermined location of the borehole is not located in the dangerous area of ​​the ancient river channel. If the burial depth of the ancient riverbed corresponding to the first predetermined location of the borehole is greater than the borehole depth, the first predetermined location of the borehole is not located in the dangerous area of ​​the ancient riverbed.

6. The preferred method for determining the drilling location of an exploration well as described in claim 5, characterized in that, The offshore exploration well drilling location corresponding to the predetermined drilling location also includes a third predetermined drilling location. After determining the drilling location, it also includes: The third predetermined drilling position is determined. According to the engineering geophysical survey report, if the horizontal soil composition characteristics of the strata at the bow leg position and the stern leg position, which are located within or outside the ancient river channel, differ significantly, the jack-up drilling platform is moved to transfer the predetermined drilling position to the corresponding third predetermined drilling position. The third predetermined drilling position is not located in a danger zone, and the bow leg and stern leg are located in the same geological structure, and the bow leg and stern leg do not cross the danger zone.

7. The preferred method for determining the drilling location of an exploration well as described in claim 1, characterized in that, When determining whether the first predetermined location of the borehole is located in a danger zone, the danger zone shall be determined in the following order: Determine whether the first predetermined location of the borehole is located in a shallow gas hazard zone; Determine whether the first predetermined location of the borehole is located in a fault hazard zone and / or an ancient river channel hazard zone and / or a submarine pipeline / cable hazard zone.

8. The preferred method for determining the drilling location of an exploration well as described in claim 7, characterized in that, The borehole location corresponding to the predetermined borehole location also includes the fourth predetermined borehole location determined by the requirements of reservoir exploration and development and the design trajectory requirements of directional wells. If it is located in a dangerous area, the displacement distance of the predetermined borehole location of the jack-up drilling platform from the first predetermined borehole location to the fourth predetermined borehole location is less than the displacement distance from the first predetermined borehole location to the second predetermined borehole location. The borehole location corresponds to the fourth predetermined borehole location.

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