Evaluating and Predicting Heterogeneous Reservoirs and Its Oil-bearing Properties by the Analysis Technique of the Diagenetic Lithofacies──Taking Hadexun area in Tarim basin as an example

Key words: 
• diagenetic characteristic /
• types of reservoirs /
• evaluation of reservoirs /
• prediction of oil-bearing properties

Abstract: Research for the diagenetic lithofacies is based on sedimentary facies, which stress on the observation of diagenetic characteristics in sedimentary rock. Diagenetic lithofacies are distinguished and defined according to the differences of secondary diagenetic textures (including components of cements, cement types, fabric of contraction and solution, pore types and its distribution, etc.). On the basis of analyzing the micro-diagenetic characteristics, the thin sandstone in the middle-mudstone member and the Carboniferous Donghe sandstone are divided into six diagenetic lithofacies. The thin sandstone is composed of the compaction mixing cement facies and the non-compaction mixing cement face; the Donghe sandstone is composed of the solution facies, the primary pore facies, the solution-primary pore mixing facies and the carbonate cement facies. The quality of reservoirs changes with different diagenetic lithofacies. By analyzing and estimating, we conclude that the solution facies is best reservoir(Ⅰ 1), the primary pore face and the solution-primary pore mixing facies is good reservoir(Ⅰ 2), the non-compact cement facies and the non-compact type in the carbonate cement facies are medium reservoirs(Ⅱ), the compact cement facies and the compact type in the carbonate cement facies are bad reservoirs(Ⅲ). On the basis of this study, 8 wells are analyzed in this area by well logs models. As a result, we can see that the distribution of diagenetic lithofacies and different reservoir types distributed vertically and horizontally. Combining distribution characteristics of solution facies and its cause with migration of oil and gas and structure characteristics, we can predict the new oil-bearing area, and propose that the two high points of trap will be favorable for driuing at northwest and southwest from YW3 well, and very likely to gain industrial oil flow.