Application of Hydrocarbon Gas Abundance Log in the Rolling Exploration and Development of Offshore Extra-low Resistivity Oilfield: A Case Study of CFD Oilfield Group in Bohai Bay Basin

Abstract

Billion barrels of oil has been proved in low resistance reservoirs of CFD Oilfield Group in Bohai Bay Basin. In this region, water is not distinct from oil as they have the same resistivity value. But in exploration stage, we identify extra-low resistivity oil zones based on nuclear magnetic logging, testing and cores. Further more the development stage, we adopt the previous knowledge about these extra-low resistivity oil zones to satisfy the production. Still we face two problems next. Firstly, besides the already known extra-low resistivity oil zones, the development wells are not able to identify new encountered ones for lacking effective and economical methods. Secondly, in later stage of development, we are not able to test our prediction of water flooding as well as remaining oil distribution with resistivity log of new wells, which means the oilfields would keep adjusting without knowledge basis in the future. In recent years, we analyze the genesis of the extra-low resistivity and select gas logging as the main material to solve these problems for its high sensitivity to fluids in this region. Because the gas logging is affected by many factors during implementation, it is not accurate enough to indicate hydrocarbon quantitatively. Thus on the basis of analyzing all factors, we write correcting formulas to eliminate their interference and take three steps of standardized work flow including single well correction, cross-hole correction and pseudomorph identification to correct the gas log into hydrocarbon gas abundance log, which has been proved being able to identify extra-low resistivity oil zones and their water flooded zones precisely. Based on these advantages, hydrocarbon gas abundance log plays a key role in the rolling exploration and development of extra-low resistivity oilfields. By reviewing the old wells’ gas logging data combining with seismic hydrocarbon detection, many oil zones in old oilfields and a couple of new oilfields are discovered; further more, writing the relational expression between hydrocarbon gas abundance and remaining oil saturation help us revise our knowledge of the remaining oil which plays a key role in maintaining production in later stage of development. In the context of current low oil price, without any additional cost, our study helps us get both success and profits in the rolling exploration and development of extra-low resistivity oilfields.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018