Abstract:

Production in the Huangjue oil field of the Subai basin,China,commenced in 1980.The field structure is a west-east trending roll over anticline.To date,only 8.7％ of STOIIP(stock tank oil initially in place)has been recovered from the Eogene Dainan Formation divided into Daiyi Member and Daier Member.Such low recoveries are due to the complex reservoir textures and to early development practices.Reservoir management studies on optimizing recovery and identifying unswept oil volume are ongoing so as to maximize the venture's profitability.The reservoirs of the Dainan Formation consist of the distributary channel,mouth-bar,overbank and sheet sand deposits of the shallow lacustrine delta deposited in the flat shore-shallow lake under the warm,wet semi-tropical climate;however,pay zones are composed of predominantly distributary channel sand bodies.The ancient streams of the Dainan Formation,as a meandering river,flowed from south to north in the early Dainan period and came from dominantly the northwestern source area.The average widths of channels and bodies in the Daier Member and Daiyi Member are 329m and 207m respectively.There servoir texture in the Dainan Formation is alabyrinth described by Weber.This texture shows the channels and bodies are isolated and lenticular.Hence,the internal communication within these pay zones is believed to be extremely bad.In addition,this texture also determines the sizes and distributions of oil sandbodies in the Dainan Fomation.This work confirms and quantifies the impact of well spacing on the recovery factor,and figures the rational well spacing of the Huangjue oil field.To acquire an optimal improvement in the recovery factor,the rational well spacing ranges from 100 m to 300m.

Key words: reservoir texture, distributary channel sandbody, oil sandbody, well spacing, the Huangjue oil field