Characteristics And Evaluation Of Chang6Reservoir In Huachi-Baibao Region Of Ordos Basin

Huachi-Baibao area in Ordos basin is a new discovered oil block of Changqing oilfield branch in recent years. Chang6Member Formation of upper Triassic is the main subject reservoir. There are rich sand body and abundant oil in this area. However the crude output is low by the influence of reservoir space distribution, sand thickness, physical property, etc. Through the research of reservoir characteristics and evaluation in Huachi-Baibao area, it is of important meaning in finding out reservoir spread underground and the spread of relatively higher porosity and permeability reservoir rock, predicting the favorable area of oil and gas, leading a scientific deployment for the further oil and gas exploration and development.Based on collecting and analyzing a lot of regional geological date, observing and measuring the outcrop, the paper systematically studies the reservoir characteristics of Chang6member, Huachi-Baibao oilfield, and predict the favorable area of oil and gas on this basin, by taking full advantage of drilling, logging, core observation, oil testing and so on, as well as fully using the various advanced testing means, such as thin-section analysis, scanning electron microscope, mercury porosimetry, X-ray diffraction and other means.Research shows that the Chang6formation in studied area is a set of lake delta deposition, and belongs to delta front subfacies. The rock types are primarily for fine arkoses. The reservoir space types are mainly residual intergranular pore. Its reservoir physical characteristics is poor. It is a ultra-low permeability reservoirs. The study on the diagenesis course indicates that diagenetic evolution is now in mid-diagenetic phase A. The sandstone had undergone compaction, pressure solution, cementation, metasomasi, dissolution and fracturing. Through analysis on the major reservoir influence factors, reservoir physical property mainly effected by sedimentary micro-facies and epigenesist. The compaction in early diagenetic period and the cementation of carbonate in late diagenetic period are primary causes which make physical property worse. But the dissolution which throughout the whole diagenetic period, and the microcrack from tectonic stress and compaction are crucial for improvement of reservoir properties. Both the intraformational and interformational heterogeneity are relatively strong. The result of laboratory evaluation on Reservoir Damage is that the reservoir mainly show low water sensibility-moderate water sensibility, low saline sensibility, moderate-weak flow rate sensibility, moderate～stong acids sensibility. The result of seepage experiment shows that Yanchang6member reservoir in the study area has a certain degree of soluble. It has the characteristics of low irreducible water saturation and relatively high residual oil saturation.Based on the study of reservoir characteristics, and with the characteristics of pore structure parameters research. The reservoir of Chang6member can be divided into class I (good) reservoir, class II (medium) reservoir, class III (poor) reservoir, IV class (poor) reservoir. The result of core analysis and log interpretation show the type of Chang6member reservoir in the study area mainly are class II and IIIThe favorable area of Chang6member oil deposit in this area were predicted according to formation coefficient, as well as the thickness of sand body and the reservoir physical property, etc, there are sever favorable areas in Yanchang63, one favorable areas in Chang62. Reliability evaluation in the predicted favorable area according to oil testing, number of exploratory well and reservoir physical properties shows that there are four most reliable prediction areas, three reliable prediction areas and one relatively reliable prediction area.