Offshore oilfield shallow gas prediction and pre-drilling scheme design method

Abstract

The invention discloses an offshore oilfield shallow gas prediction and pre-drilling scheme design method. The method comprises the following steps: obtaining a gas cloud area distribution range and a top surface depth; the distribution positions and the top surface depth of a plurality of bright spots of shallow gas with the altitude depth being 500 m or above are obtained; according to the gas cloud area distribution range and the distribution positions of the multiple bright spots of the shallow gas, the depth and coordinates of the gas cloud area and the shallow gas drilled by the development well trajectory are designed and counted; a pre-drilling scheme is designed according to the depth and coordinates of the gas cloud area and the shallow gas drilled by the development well trajectory; and the pre-drilling scheme is optimized. According to the offshore oilfield shallow gas prediction and pre-drilling scheme design method disclosed by the invention, various factors such as the quantity, the position, the orientation and the depth of the drilling shallow gas are comprehensively considered, pilot wells and pre-drilling wells are screened, and a pre-drilling scheme for implementing the risk of the shallow gas is designed and formed.

Description

technical field [0001] The invention relates to an offshore oilfield shallow layer gas prediction and pre-drilling scheme design method, which belongs to the technical field of offshore oilfield development. Background technique [0002] Many oilfields in the Bohai Sea area of ​​my country develop large-scale gas cloud areas. Due to the uneven distribution of escaped gas in the "gas cloud area", shallow gas presents a state of either accumulation or dispersion in shallow formations. Shallow gas blowout accidents are extremely harmful. Shallow gas is relatively developed in the Bohai Bay Basin, and shallow gas blowout accidents occur from time to time. Compared with land drilling, offshore drilling has the characteristics of high investment and high risk. Therefore, for oil and gas fields with high risk of shallow gas, it is necessary to explore a shallow gas prediction method and pre-drilling plan suitable for offshore drilling, so as to effectively prevent shallow gas The ...

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Problems solved by technology

[0003] At present, the research on the prediction of shallow gas and gas cloud areas in offshore oilfields is still weak, and the data used is relatively single. Only engineering geophysical data or 3D seismic data are used alone, and the results of the two have not been comprehensively analyzed and applied.

Moreover, the prediction results of shallow gas and gas cloud areas are not well integrated with the drilling plan. The design of drilling trajectories is generally based on avoiding risks, and the adjustment and optimization of follow-up well trajectories after confirming the distribution of shallow gas and gas cloud areas by pre-drilling and other modes are not fully considered.

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