Study Of Fluid Identification By Combining Logging With Geochemistry Of Supra-basement Sand Reservior

Supra-basement sand body is located at the northwest part of the Huimin Depression, which is about 400km2. Because the area of Supra-basement sand body, which drilled at sedimentary facies zone, is mainly delta-front facies with fine siltstone. It is interbedded with charcoal grey mudstone with high heterogeneity. The sand rock is of high shale content and common and strong quartz overgrowth, which leads to bad-developed inter granular space, the average porosity is 14.1%. The reservoir quality is relatively bad, mainly with low porosity, low permeability and low resistance. The above characteristics lead to be difficult to identify water or oil bed and limit the upgrade of reservoir. There is a prominent problem in the evaluation of Supra-basement sand reservoir, namely oil-water layers discrimination.The Geochemistry uses reservoir core sample or the side-wall coring sample to carry on the pyrolysis analysis, the thermal decomposition chromatograph analysis, and the good chromatograph analysis. It distinguishes oil and water level from the quota and qualitative aspects, so it has a direct and low-cost advantage. The use of Nuclear Magnetic Resonance Logging to identify oil, gas and water lever by the differences of nuclear magnetic resonance nature of liquid. The above two methods all have very high accuracy. At the same time, the NMR logging has the superiority over conventional logging. It can not only determine the nature of fluid reservoir, and can provide quantitative parameters such as porosity, permeability, free water, mud bound water, capillary bound water and hydrocarbons. While the capillary bound water is one of the important reasons of low-resistivity reservoir. As a result, nuclear magnetic logging in this area of low permeability reservoir evaluation is of great significance.Though geology generalization research ,which is proceeded from core by using geochemical analysis technique and nuclear magnetic resonance logging, it is built up the criterion of identifying oil, dry and water. Thereby it is developed the mature identification method of low- permeability reservior.The result and recognition is obtained from Supra-basement sand reservior: 1. Make use of the NMR logging and conventional logging to research the model of reservoir factors at the basis of core data is not only developed the accuracy of interpretation of reservoir factors, but also laid the foundations of identification of reservoir fluid accurately.2. Because of reservoir densify, high irreducible water saturation, low oil saturation and little difference between oil and water, it is difficult to indentify reservoir fluid by conventional logging. In the paper, consuming the feature of the NMR logging, which can directly explore hydrogen content of reservoir fluid, and combining with conventional logging, it is indentified reservoir fluid effectively.3. Though a directly analysis of the organic fluid of the reservoir sample by geochemistry, it is developed the accuracy of identification of low-permeate reservoir.4. Though geology generalization research ,which is proceeded from pore structure by using geochemical analysis technique and nuclear magnetic resonance logging at the basis of multiple data and method, it is developed the mature identification method of low-permeability reservoir which is significant popularization of the analogous reservoir in future.