下寺湾油田长8致密油有效储层识别及地质“甜点”优选

Effective Reservoir Identification and “Sweet Spot” Optimization of Chang-8 Tight Oil Reservoir in Xiasiwan Oilfield

以下寺湾油田长8油藏试油、试采及生产数据为基础,识别在水平井加大规模体积压裂技术条件下能够开发的储层为有效储层,从岩心特征、岩屑气测综合录井特征、储层试验分析和测井响应特征等方面建立有效储层的识别标准。认为在现有技术条件下下寺湾油田能够开发的致密油储层为孔隙度大于8.5%、渗透率大于等于0.15mD的油迹级以上细砂岩。储层含油饱和度大于等于30%,测井响应声波时差大于等于222μs/m。全烃气测录井气测值为基线的5倍以上,电阻率达到32Ω·m以上,且压裂后可动用油层厚度达5.0m以上的识别为地质"甜点"区。地质"甜点"区的筛选按照先从致密油"三大控制因素"进行有利区带优选,然后用重新确定的有效储层下限标准进行"甜点"筛选,在油藏内部产能建设实施过程中按照含油性、油层的有效厚度及邻井实施效果排序,排除风险区,避免低效区。

We proposed criteria whereby tight oil wells can obtain industrial oil flow under the technical conditions of large-scale volume fracturing of horizontal wells based on the well test results and dynamic production data for Chang-8 tight oil reservoirs in Xiasiwan oilfield.The criteria were established using core observation,comprehensive logging characteristics of cuttings gas survey,reservoir analysis,and well-logging response.We found that the effective fine sandstone formation has porosity is equal or greater than 8.5%,and permeability is equal or greater than 0.15 mD.In the “sweet spot” zone,the oil saturation of reservoir is equal or greater than 30%,the interval acoustic transit time in well logging is equal or greater than 222 μs/m,the full hydrocarbon gas logging value is more than 5 times of the baseline,the resistivity is greater than 32 Ω·m,and after fracturing,the thickness of usable oil layer is more than 5.0 m.Firstly,according to the “three major control factors” of tight oil reservoir,the favorable zone selection was carried out,and then the redefined effective reservoir lower limit standard is used to make “sweet spot” zone selection.During development,the oil saturation,the effective thickness of the reservoir and the effect of adjacent wells were considered for reducing the risk of low yield or low efficiency areas.