柴达木盆地西部地区复杂碳酸盐岩储层流体识别新方法

New Method for Fluid Identification of Complex Carbonate Reservoirs in Western Qaidam Basin

柴达木盆地西部地区新生代咸化湖盆滨浅湖沉积的碳酸盐岩具有明显的混积特征,储层岩石矿物成分多样,砂、泥、碳酸盐矿物同时存在,具有晶间孔、溶蚀孔及微裂缝等多种储层空间类型,孔隙度较小、孔隙结构较复杂,储层具较强非均质性,传统的测井评价方法难以对流体进行有效识别。针对柴达木盆地近几年勘探发现的干柴沟、英西、风西及南翼山等重点区域的混积碳酸盐岩储层,基于岩性扫描、介电测井、二维核磁共振等特殊测井技术,提出了热中子及氯离子含油指示、介电参数及介电含水饱和度、核磁共振T1—T2交会图等流体识别方法和多维度相结合的流体识别思路。实际应用表明,该方法及思路有效地解决复杂碳酸盐岩储层流体识别难题,提高了解释符合率。

The carbonate rocks deposited by shallow lakes in the Cenozoic salty lake basin of the western Qaidam basin are characterized by obvious mixed accumulation.The mineral composition of the reservoir rocks is diverse.Sand,mud and carbonate minerals coexist.There are many kinds of reservoir space types,such as intergranular pores,dissolution pores and micro fractures.The porosity is low,the pore structure is complex,and the reservoir has strong heterogeneity.It is difficult to identify the fluid effectively by traditional log evaluation methods.Study areas are the mixed carbonate reservoirs in Ganchaigou,Yingxi,Fengxi,Nanyishan and other key areas discovered in recent years in Qaidam basin.Special logging techniques such as lithology scanning,dielectric logging and two-dimensional nuclear magnetic resonance are used in study areas.We propose fluid identification methods such as thermal neutron and chloride ion oil indication,dielectric parameters and dielectric water saturation,nuclear magnetic resonance T1—T2 intersection diagram,and a combination of multi-dimensional fluid identification ideas.The practical application shows that methods and idea can effectively solve the problem of fluid identification in complex carbonate reservoirs,and improve the interpretation coincidence rate.