钻井现场综合信息在发现Belketaief气藏隐蔽气层的应用

Application of Comprehensive Information at Rig Site on Discovering the Subtle Gas Bearing Reservoirs in Belketaief Gas Reservoir

钻井现场的工程数据,如泥浆密度、地层压力、钻时气测值、循环后效气等,由于主要被作业人员用于现场井控,而往往不被室内测井、地质解释研究人员所重视。实际上,对于比较活跃的油气层,在钻井以及测试过程中,通常会通过工程参数的异常变化表现出来。以中油国际(CNPCI)阿尔及利亚勘探项目Belketaief高产气藏的勘探发现为实例,把钻井工程数据与测井、试油数据相结合,通过分析钻井泥浆与压井泥浆密度差异,分析色谱仪记录的压井循环后效气测数据,并经过与测井图对比,发现气测异常井段与本井各套砂层组之间存在很好的位置对应关系。同时,对比钻时气测值与循环后效气测值,利用电缆地层测试获取准确的压力剖面,逐一监测单砂层流动性,最后成功找到一套测井资料解释时漏失的低电阻高产油气层,挽救了一个濒临废弃的老区块。将后效气测色谱记录的数据、钻时气测值与压井循环后效气测值和其他工程数据,融入到对油气田勘探的综合评价中,可以从不同角度审视油气藏的内在特征,有助于识别和发现隐蔽的油气藏。

Drilling engineering data,such as mud weight,formation pressure ,trip gas and circulation gas chromatography ,etc. ,are commonly used at rig site for well control by drilling group ,which are often ignored by in house study group of logging and geologic interpretation.Actually,those active hydrocarbon reservoirs may present themselves through abnormal change of engineering data at rig site soon after being drilled open and being tested.This paper introduces a successful case study of how a high productivity gas reservoir has been discovered by CNPCI at Algeria exploration blocks.Circulation gas chromatography of well killing is analyzed after the analysis on density difference between drilling mud and kill mud combined the drilling engineering data with well logging and oil test data.Good position correspondence is then discovered between the intervals with abnormal gasometry and each set of sand group in the same well through the comparison with the well log.Flow properties of single sand body are monitored one after another based on accurate pressure profile got by wireline formation test and the comparision of trip gas and circulation gas chromatography.Through comprehensive analysis and feasible operation planning,we retrieve a missing low resistivity but high produc- tivity gas zone which are not recognized on log interpretation procedure.Thus the life of an old block being abandoned is saved.The successful application of drilling engineering data in this case provides good experi- ence which may guide subtle gas reservoir exploration in the future.It is useful for understanding the intrinsic characteristics of the hydrocarbon reservoirs and discover the blind zone or reservoir when the chromatogram data of trip gas and circulation gas ,formation pressure ,fluid density and other drilling engineering data are combined with wireline data and geologic background to analyze and evaluate the potential in the exploration.