Research On Well-logging Evaluation Method Of Water-Flooded Zone In Daqing L Oil Field

Continental deposit is the basic characteristics of china field geology. China is the world’s terrestrial oil major oil producing countries,95%of its crude oil production comes from continental. Most oil field adopt water flooding program, water-flooded oil reserves has87%of total reserves. Most oil fields already in multi-well, multi-layer, multi-direction water flooding phase, oil fields has more than80%of the average water content, the wells that water content of more than60%have been over half of the total. Particularly in the eastern part of China, water distribution often changes, as the formation heterogeneity, and extent of inequality into the waves. Most oil fields have successively entered the high water cut stage and production decline period. The national land-based oil field reached an average of81.4%moisture content. But the extent of recovery of crude oil averaged only21.7%, and recovery is relatively low. In the oilfield production tail, although a large number of oil and gas had been taken out, but there is still a considerable number of remaining oil and gas in different size, forms and irregularly distributed in the modified. In response to this phenomenon, to enhance the oil recovery, mining oil remaining reserves, we need to identify the injected of the low level recovery of remaining oil-rich region that water does not spread to, and estimate the remaining reserves, to supply basis to the adjustment of oil field development program, and just logging in this area has its unique advantages. Relative to other methods, well logging is the method that takes the largest information collected through the pit shaft and sampling density, as well as it can reflect real-time formation of the size and change of various parameters. And logging costs are lower the use of logging methods for evaluation of flood level and production of oil field development phase of monitoring has become an indispensable tool.After30years development, Daqing L Oilfield through six stages of the flowing mining, strata adjustment, full conversion pumping, injection system adjustment, the second main reservoir infill and polymer flooding in major reservoirs. at present, the composite water cut reached90%above, has entered the development phase of high water cut stage, the remaining oil distribution is extremely fragmented. The results show that:Although thick oil fields in L all see water, but the weak, not washing still about30%. Remaining oil and the flooding in thick oil layer Alternate with distribution. Especially for the study area, the long-term water injection and polymer flooding, fluid properties, pore structure, physical and chemical properties of rock and oil-water distribution in producing formation have undergone some degree of change, many of the main layer of water flooding degree is serious. Fluid distribution of reservoir is complex, and the remaining oil distribution in the layers and in interlaminations have great differences. In the same layer, as the effect of reservoir heterogeneity and the sedimentary rhythm, weak and strong water flooded state storage; Because of difference in reservoir properties, water flooding state is more complicated; Polymer on the impact to the electrical properties of reservoir, conductive mechanism and water flooding has some differences, at present the use of logging data to determine residual oil after polymer flooding reservoirs is not perfect. Some of the original log interpretation methods can not meet the L region log interpretation, as well as the original definition of the standard flood level are difficult to adapt to the need for adjustment of the high water cut Encryption field. We must be re-summarized log response characteristic which meet the water flooding and polymer flooding development phase in water flooded zone, re-adjustment and added interpretation technique for the oil field, provide technical support in infill well spacing, injection relationship adjustment, profile control, water control to in order to achieve rational and efficient development of oil field goal.In this paper, water flooding, development of oil fields flooded layer polymer injection log interpretation as the core, the remaining oil distribution and the reservoir for the purpose of quantitative evaluation as the goal, we use the impact of factors from the flood level, flooding mechanism, this paper integrated analysis reservoir water flooding and polymer flooding in the development phase of such reservoir lithology, porosity, permeability, wettability, formation water salinity and other changes, summed up the oil in the fresh water flooding, sewage water flooding, polymer flooding, and other development phase changes of the physical properties and logging response characteristics.At the same time, in view of the complex nature of fluid characteristics in water-flooded layer in Daqing L field, we proposed analysis technology in various flood Logging identification and comprehensive in system, and used core data and a variety of methods to establish the flood level of porosity, permeability, saturation, and water production rate and other explanatory models, built from qualitative to quantitative evaluation method of flooding the interpretation of layer, and then flooded layer is given by the five-level standard, in the last used application of Bayes discriminant, Fisher discriminant and the three BP neural network types of discriminant analysis, effectively divided flood levels in the region, with the core analysis results of comparison, the rate of three methods to determine compliance. According to the flooded field characteristics of L oil field and the above research results, we developed a flooded layer process, actually processed more than ten wells, and to explain more than85%accuracy. Porosity, permeability, water saturation, irreducible water saturation to these parameters are good agreement with the results of core analysis, but the water production rate, oil displacement efficiency has yet to be put into operation, inspection, and improve. This research can play a guidance and reference the evaluation to the other oil fields in Daqing that flood high water level.