基于CQ指标的长庆油田长6—长8段致密油储层划分标准研究

鄂尔多斯盆地三叠系长6—长8段致密油储层具有低孔、低渗、低压和低产等特征，为了优选单井剖面的地质甜点、工程甜点，针对长6—长8段致密油储层的地质特性，提出了一种划分致密油储层标准的实用方法。首先计算或提取储层的最小水平主应力、破裂压力、脆性指数、孔隙度、渗透率及含水饱和度等参数，建立储层完井品质综合评价指标CQ；然后基于CQ和单井产能的关系图版，将储层划分为好、中、差3个等级，并根据CQ值优选射孔压裂层段。利用该方法对长庆油田陇东地区L375井进行了储层划分，划分结果与试油结果对比表明，基于CQ指标优选出的射孔压裂位置与实际高中低产井段完全相符。研究表明，该方法满足优选致密油射孔压裂位置和寻找地质甜点、工程甜点的要求，可以用于区块储层的划分。 

The Standard Division of Tight Oil Reservoirs in Chang 6-8 Members of Changqing Oilfield based on CQ Index

The tight oil reservoirs in the Chang 6-8 Member of the Triassic Yanchang Formation in the Ordos Basin are characterized by low porosity, low permeability, low pressure and low production. In order to optimize the geological engineering sweet spots on the single-well section, a practical method for standard division of tight oil reservoirs has been proposed in accordance with the geological characteristics of Chang 6-8 tight oil reservoir. The first step involved calculating and extracting the minimum horizontal principal stress, fracture pressure, brittleness index, porosity, permeability and water saturation of reservoir etc. This allows them to establish the comprehensive evaluation index of the reservoir completion quality (CQ), and then, to classify the reservoirs “good, medium and bad” based on the relationship chart of CQ and single well productivity. And then to optimize the perforating and fracturing intervals in terms of the CQ value. Using this method, reservoir division was performed in Well L375 of the Changqing Longdong Area, and the comparison of division result and the oil test result showed that the perforating/fracturing interval optimized by the CQ index was completely consistent with the actual intervals of high, medium and low production-yields. Study results also indicated that this method could meet the requirements for optimizing the perforating/fracturing intervals of tight oil and and for identifying engineering geological sweet spots, and can be used for a classification standard for block reservoirs.