基于成因机理的低阻油层精细评价方法

Low-Resistivity Oil Layers Fine Evaluation Approaches Based on Mechanism

低阻油层已成为各油田现阶段增储上产的主力储层之一。通过对葡敖油田葡萄花低阻油层的研究发现,构造和沉积特征在宏观上综合控制着该区低阻油层的形成和分布。对构造而言,低阻油层主要发育在低幅度构造的鼻状构造两侧的西部斜坡带、平缓斜坡带;对沉积而言,低阻油层主要发育于弱水动力条件下形成的三角洲前缘的席状砂及滨浅湖的滩砂和坝砂中。在宏观地质因素控制下,低阻油层的微观特征表现为高地层水矿化度、高束缚水饱和度和强黏土矿物附加导电。基于岩心和测井数据,针对低阻油层的实际特征,利用储层品质因子代替传统经验公式中的孔隙度建立束缚水饱和度模型,根据阳离子交换能力和黏土矿物含量的特征,构造该区低阻敏感参数,建立低阻油层评价的高精度数学模型;并依据分析化验数据综合确定各特征参数在低阻油层的下限值,实现从定性识别向定量评价的过渡。利用低阻油层的定量评价模型精细解释研究区17口关键井,能准确识别26个低阻油层中的25个,获得了96.15%的准确率。

The low resistivity oil layer has become one of the main reservoirs for increasing reserve and production for each oilfield.After the research of Putaohua low-resistivity oil layers in Puao oilfield,we find that the forming and distribution of low-resistivity oil layers are controlled by structure characteristics and sedimentary characteristics.In term of structure,low-resistivity oil layers mainly develop in the west ramp region and flat gradient region on two sides of nosing structure.In term of sedimentary system,low-resistivity oil layers main develop in the delta front sheet sand,and beach bar sandstones of shore-shallow lacustrine which formed in weak hydraulic condition.Under the control of macro-geologic factors,the micro-geological characteristics of low-resistivity oil layers are high bound water saturation,high salinity formation water and the added conductivity of shale.Base on core and logging data,aiming at the actual characteristics of low-resistivity oil layers,we choose quality factor instead of porosity of tradition experience formation to compute bound water saturation.According to the characteristics of cation exchange capacity and shale,we construct low-resistivity sensitive parameter and build high accuracy model of low-resistivity evaluation,then,determine the lower limit value of each parameters based on the test data.It makes the quality identifying turn to quantity identifying.The method has been applied in this area for evaluating 26 low resistivity formations of 17 wells,and it identified 25 of them.It obtains 96.15% rate of accuracy.