二维核磁共振测井在致密碳酸盐岩储层中的应用

Application of 2D NMR Log Data in Tight Carbonate Reservoirs

鄂尔多斯盆地致密碳酸盐岩储层存在岩石组分复杂、孔隙非均质性强,储集空间类型多样的特点,基于常规测井资料计算的储层参数可靠性差,难以准确识别储层流体性质。为提高致密碳酸盐岩储层流体性质识别,研究黏土束缚水孔隙、微细-中孔、粗孔-孔洞3种孔隙组分的核磁共振横向弛豫时间特征,利用核磁共振测井T2分布计算3种孔隙组分的孔隙度,建立T1、T2几何平均值比值与粗孔-孔洞孔隙度流体性质识别图版,微细-中孔孔隙度与粗孔-孔洞孔隙度储层有效性评价图版。对致密碳酸盐岩储层流体性质判识结果表明,二维核磁共振测井对致密碳酸盐岩微细-中孔型及粗孔-孔洞型储层流体识别效果较好,针对孔隙不连通储层及裂缝性储层应用存在局限性。

Tight carbonate reservoirs in the Ordos basin are characterized by complex rock composition,strong pore heterogeneity and diverse types of reservoir space,so the reservoir parameters calculated from conventional log data are less reliable,making it difficult to accurately identify reservoir fluid types.In order to determine the fluid types of the tight carbonate reservoirs,this paper studies the transverse relaxation distribution of clay-bound-water pores,micro-meso pores and caverns,then calculates their porosity,and finally builds the fluid type crossplots with the ratio of T to T geometric mean and coarse and cavernous porosity,and the effective evaluation charts of micro-meso and cavernous porosity.Applications have proven that 2D NMR logging data are effective to identify the fluid types in tight carbonate reservoirs with micro,meso,coarse and cavernous pores,but they are relative limited in the reservoirs with disconnected pores and fractures.