Research Of Identification Method To Oil Reservoirs With Low Resistivity Caused By High Content Bound Water With Well-log Data In Jiyuan Area

With the deepening of the exploration of the global oil and gas, the hydrocarbon reservoirs with low resistivity are extensively being paid attention to. Earlier product logs are usually in their late period because of the increasing of the water content ratio in many oil fields, and it is difficult to develop the potential ones and to increase production. So to these special hydrocarbon reservoirs with low resistivity, it is a little-investment method which can take effective in short period for looking for new hydrocarbon reservoirs and increasing the reserve only to need to seriously research the former data and do the secondary development well. In these recent years it has been a difficult problem for experts to identify and evaluate the hydrocarbon reservoirs with low resistivity in handling and explaining field with well-log data.The Chang-2 hydrocarbon reservoir with low resistivity was analyzed in JiYuan area of ChangQing oil fields. The Four characteristics (lithological, physical, electrical and oil bearing characteristics) of the Chang-2 reservoir and their relationships with each other were researched detailedly. According to the oil bearing condition and oil reservoir's characteristics, the conclusion is that the reservoir has these characters: the small-size lithology, complex relationships of the porosity and permeability, low resistivity.Based on the analysis of factors which make this reservoir's resistivity low, the conclusion is that: high-content bound water is one of the main reasons of the reservoirs' low resistivity. Some reservoirs were identified qualitatively and the main causes of the high-content bound water were researched and discussed, and concluded that the high-content bound water in the Chang-2 reservoir was mainly caused by the factors as: the small size of grain of the rocks, the complex pore texture and the thin pore throats etc.The values of the main factors (the porosity, the granularity and the content of the clay) of the reservoir were quantitatively computed using the data of the previous analyzed well-log and logging data and contrasted with corresponding factors which came from the measurement in laboratory. The degree of the fitting is 93.26%, and thefine fits produced the reliable factors to exactly evaluate the hydrocarbon reservoirs with low resistivity.The qualitative chart interpretation for identifying the Chang-2 reservoirs' low resistivity in this area was made and the chart can be used to distinguish the reservoir's character of oil bearing. It may re-differentiate the logging conclusion using the saturation of the movable water concluded. With the new chart, identifying the reservoirs and comparing with the result of the oil test increased the rate of the interpretation accuracy.The saturation of the bound water was quantitatively concluded with the relational mode of the bound water's content, porosity and permeability. Using the Method of Movable water Analysis, the content of the movable water in the reservoir's pore which reflected the reservoir's oil character indirectly was researched, and the fine result was gained by identifying the target interval.