塔中西部奥陶系碳酸盐岩储层定量评价方法研究

塔中西部奥陶系碳酸盐岩储层分布面积广、厚度大,多年勘探发现了一批奥陶系碳酸盐岩缝洞型油气藏,是塔里木盆地下步勘探开发的重要目标。由于碳酸盐岩储层多与岩溶作用相关,优质储层在地震剖面上表现为“串珠状”异常的地震反射特征。这些“串珠状”地震异常反射在地震波形、振幅能量等地球物理参数上不尽相同,往往指示着碳酸盐岩储层发育程度的差异性,以前作法是在一个包含储层发育段时窗内,提取振幅能量属性,定性认为振幅能量值高,储层发育,反之振幅能量值低,储层不发育。为此提出一种储层发育指数计算公式,给出了定量评价碳酸盐岩储层发育程度方法思路,根据研究区已钻地震“串珠”井解释成果,确定出研究区储层发育指数大于17500,波谷振幅能量大于9000区域为高效区,落在该区内的“串珠”井钻探储层发育,试采情况很好,均为高效井;储层发育指数大于17500,波谷振幅能量小于9000区域和储层发育指数小于17500,波谷振幅能量大于9000区域为有效区,落在该区内的井钻探“串珠”储层较发育,试采情况良好,为有效井;储层发育指数小于17500,波谷振幅能量小于9000区域为低效区,落在该区内的“串珠”井钻探储层欠发育,试采情况较差,为低效井。研究成果有利于指导碳酸盐岩稳产高产井位部署。

METHOD RESEARCH OF QUANTITATIVE EVALUATION ON ORDOVICIAN CARBONATE RESERVOIRS IN WESTERN TAZHONG AREA OF TARIM BASIN

A number of Ordovician carbonate fractured-cavity reservoirs have been discovered for many years,the Ordovician carbonate reservoirs in western Tazhong area of Tarim Basin have a wide distribution area and a large thickness,so it’s an important target for the next exploration and development in the Tarim Basin.Since carbonate reservoirs are mostly associated with karstification,high-quality reservoirs appear anomalous seismic reflection features as"string beads"in seismic profiles.These"string beads"seismic anomalies reflect differences in geophysical parameters such as seismic waveforms and amplitude energy,and often indicate the differences in the degree of development of carbonate reservoirs.The previous practice was to extract the amplitude energy properties in a time window containing reservoir development segments,and it is qualitatively assumed that the reservoir is developed if the amplitude energy value is high,whereas the amplitude energy value is low then the reservoir is not developed.To this end,a calculation formula for reservoir development index is proposed,and a method for quantitatively evaluating the development degree of carbonate reservoirs is given.Based on the interpretation results of the"string beads"in the drilled-well study area,it was determined that the development index of the reservoir in the study area which was the high-efficiency was greater than 17,500,and the energy of the trough amplitude was greater than 9000,they are high-efficiency wells in this area appearing in the developed"string beads"reservoir and the good test production;the area in which reservoir development index is greater than 17500,trough amplitude energy is less than 9000 area and reservoir development index is less than17500,trough amplitude energy is greater than 9000 is effective,and wells drilled in this area have more developed"string beads"reservoirs as well as good test production situation,therefore they are effective wells;if the reservoir development index is less than 17500,and the trough amplitude energy is less than 9000,the area is inefficient,and the wells in this area have underdeveloped"string beads",and their test production is poor,so they are inefficient wells.The research results are conducive to the guidance of well location deployment for stable production of high-production in carbonates.