The Research Of Water Flooded Layer Interpretation Method Based On Petrophysical Facies

Recently, most oil fields in our country have entered a period of high water cut with the deepening and development, the distribution of remaining oil is complex. At the same time, reservoir has been modified and reservoir heterogeneity has been enhanced along with the water injection development. The early water flooded layer evaluation method is no longer applicable. Moreover, with the continuous decrease of world oil resources, the geological conditions of oil workers faced is becoming more and more complicated. The above factors directly led to the water flooded layer evaluation work difficult. In the current stage, targeted to establish a set of fine, suitable water flooded layer evaluation method for oil field development characteristics is the basic means to realize stable oil field production, increase production. Therefore, it is very necessary to carry out the comprehensive interpretation method research of water flooded layer.L oilfield is the largest proprietary oil field of CNOOC, I period put into production in 1993, and in 2002 reached the peak of 12500 cubic meters per day, then water cut rise, the output decline. Ⅱ period put into production in 2000, the water injection has been being developed for 21 years, comprehensive water cut is up more than 70%. The crude oil of L oil field is heavy oil, the contradiction between layers is serious, phenomenon of injected water breakthrough is obvious, heterogeneity is strong, water injection system is complex. To control water and stabilize oil and avoid strong water flooded layer, it is essential to carry out the comprehensive evaluation research of the water flooded layer through technical research study according to the actual characteristics of oil field, which is helpful to predict the distribution of oil and guide the further exploration of the residual oil. This paper is based on the actual geological conditions of L oilfield. With the method of petrophysical facies classification, a detailed interpretation work of water flooded layer in the studied area has been done through analyzing actual data on the spot. Main achievements and recognition obtained as follow:(1) The reservoir in the study area was divided into Ⅰ, Ⅱ,Ⅲ, Ⅳ, a total of four types of reservoir, through a detailed analysis of reservoir physical property data and logging data, combined with regional geological condition in the study area. I type of reservoir are the best reservoir, which give priority to the upper of mouth bar and underwater distributary channel. Ⅱ type of reservoir, the physical property of which is poor than I type of reservoir, give priority to lower part of mouth bar and the upper of distal bar. Ⅲ type of reservoir, the physical property of which is poor than II type of reservoir, give priority to the lower part of mouth bar and distal bar. Ⅳ type of reservoir, the physical property of which is worst, give priority to tributary bay.(2) A good correlation between resistivity and reservoir effective porosity has been found based on the analysis of reservoir resistivity and the reservoir physical property parameters, thus established the original formation resistivity inversion model in the study area.(3) According to the established standard of petrophysical facies classification, the electrical parameters model and the oil-water relative permeability model of every kind of reservoir was established through classification process of electric experimental data and oil-water relative permeability data. There is a big difference between various kinds of rock electrical parameters, and so does the relationship between oil-water relative permeability as the change of water saturation.(4) The formation water in L oilfield is complex. The early injection water is seawater, sewage was injected lately and the water injected is the water from Guantao formation present. In view of the characteristics in the study area and starting from conductive mechanism of the formation, a set of dynamic evaluation method, on the basis of petrophysical facies, has been established to compute mixture formation water resistivity of water flooded layer, which laid a foundation for quantitative comprehensive interpretation of water flooded layer.(5) Through the part of the new drilling adjustment Wells in the study area, a comprehensive analysis found that the residual oil in the study area mainly controlled by sedimentary rhythm, well spacing, fault. Through the part of the new drilling adjustment Wells in the study area, a comprehensive analysis found that the gravity of water act dominant role in inverse rhythm formation, permeability ratio of which is less 5. This leads to the middle and lower part of formation severely flooded and residual oil mainly distributed at the top. While The reservoir physical properties act dominant role in inverse rhythm when the formation permeability ratio is greater than 5, which performed that the middle and upper part of formation are severely flooded and residual oil mainly distributed at the middle and lower part. The middle and lower part of positive rhythm reservoir and homogeneous rhythm reservoir are severely flooded and residual oil mainly distributed at the top.