柴达木盆地昆北地区基岩储层裂缝特征

Fracture Characteristics of Bedrock Reservoir in the North-Kunlun Faults Zone,Qaidam Basin

通过对柴达木盆地昆北地区8口重点井共计55.89 m长基岩段岩心的观察,统计了岩心裂缝的产状、类型、频数及分布特征,并结合岩相学、物性以及钻井、录井、测井等资料,在岩心裂缝标定测井资料的基础上,拾取基岩裂缝发育处的测井响应特征,构建对裂缝响应更为灵敏精准的新参数曲线,识别出昆北16口井基岩段247个裂缝,最后在裂缝识别的基础上分析其分布规律。结果表明：昆北基岩具有垂向分带特征,顶部为原地堆积物理风化而成的残积段,厚度0～60 m,裂缝类型以差异风化缝为主;中部为部分风化基岩段,厚度40～180 m,该段厚度在区域上变化较大,主要发育节理缝和溶蚀孔缝,是基岩中孔缝发育物性最好的储层部位;底部为新鲜基岩段,仅存在极少数的构造缝。计算裂缝分布参数表明,裂缝密度和裂缝发育率随着井点与断裂距离的逐渐变远都呈减小趋势,但裂缝密度这种减小的反相关性明显低于裂缝发育率,分析认为这可能与裂缝密度受断裂以外其他因素的共同影响有关。

This paper studies the macro and micro features, types, and distribution patterns of fractures by means of well logging interpretation, core observation, identification and well logging imaging. Based on detailed observation of 8 well with a total length of 55.89 m, we count up the number, occurrence and distribution patterns of fractures in northern Kunlun bedrock reservoir, Qaidam basin. By means of calculating parameter and fitting new logging curve, we identified 247 fractures from basement section of 16 wells. The results show that the reservoir space in the upper residual section is weathering fracture dominating which caused by heterogeneous physical property of different lithology, the ttlickness is 0 m to 60 m. The medium section under the c.rust bedrock shows the best reservoir capability, the reservoir space mainly consists of joint fracture and dissolution eaves, with a thickness of 40 m to 180 m. Only a few structural fractures occur within the bottom fresh bedrock. Based on evaluation parameters distribution, the fracture frequency and development ratio is controlled by distance to the faults, while the fracture frequency displays insignificant negative correlation with the distance than the fractures frequency which was controlled by variable factors.