Study On Distribution Law Of Remaining Oil In Wenchang 15-1 Oilfield

Offshore oil production is an important part of the domestic oil production. With the high-speed continuous development of offshore oil fields, their major reservoirs have already entered the medium-high water cut stage. China’s offshore oil fields have mainly taken the form of natural water drive development, coupled with the impact of reservoir heterogeneity, oilfield remaining oil distribution law becomes more complex; In this case, over80%of the remaining oil is not extracted from the underground, it is even more necessary for us to study the offshore oilfield remaining oil distribution law and the excavation schemes. This thesis intends to solve the following key issues:The remaining oil distribution law and the corresponding potential tapping schemes of the natural water flooding and reservoir heterogeneity offshore oilfields in the medium-high water cut stage.In this paper, take the oilfield of Wenchang15-1with the characteristics of complex geology and bottom water as an example. By means of the reservoir engineering and numerical reservoir simulation method, combined with the reservoir static and dynamic data, analyzed the remaining oil distribution law of Wenchang15-1oilfield, and located the rich areas of the remaining oil. Then put forward the potential tapping schemes of thickening well pattern and optimizing extraction, and predicted the potential tapping effects. The main research contents are as follows:(1) Analyze the characteristics of geology, reservoir stratum, oil reservoir and development of the target oil fields, and understand the current production situations and the existing problems.(2) By analyzing the definitions of reserve and production ratio and reserve replacement ratio and considering the new recoverable reserves, derived the calculation method of remaining oil saturation in the various development stages of oilfield (growth, stable and decreasing). Based on the A type water flooding characteristic curve, and oil-water relative permeability data, the quantitative interpretation methods for the remaining oil saturation and the water flooding characteristics are obtained. Considering the relationship between the cumulative fluid production and cumulative oil production under the logarithmic coordinate, the B type water flooding characteristic curve method is introduced to quantitatively interpret the remaining oil saturation. The above three methods were applied to calculate the remaining oil saturations of oilfield region and each layer of the single well in the oilfield of Wenchang15-1.(3) Based on the characteristics of bottom water flooding and edge water flooding of Wenchang oil field15-1, by means of the geologic models, a mechanism model of the remaining oil distribution law for single wells is built, and the influence of the horizontal section of the wells in vertical direction, the reservoir rhythms, the vertical heterogeneity, the layers and the water body size on the remained oil distribution is also analysed. The reservoir variation can influence the exploration ratio, such as high exploration ration for negative rhythms, low exploration ratio for positive rhythms, a better exploration ratio of integrated negative rhythms to the positive ones. Different vertical permeability usually means a different distribution of the remaining oil.(4) The reservoir of Wenchang oil field15-1and the oil remaining distribution of the charged wells are studied by the specific geological model simulating the historical production and the numerical simulation method. The simulation shows that, the untouched area and the top structure of Wenchang oil-field15-1reservoir have a lot of oil remained. Reserves abundance is concentrated in the area between A4H and A5H, and the northwest A2H and A3H.(5) According to the current distribution situation of the remaining oil in the oilfield of Wenchang15-1, the remaining oil can be recovered by liquid abstraction optimization and well increasing method. It is predicted that more abstracted liquid will result in a better recovery. When increasing wells, not only the remaining oil saturation and reserves abundance target wells, but also the abundance of the formation energy should be taken into account.