Study On Horizontal Well Productivity And Its Rational Parameters In Bottom Water Reservoir

Bottom water reservoir is in a large proportion of the reservoir in China. It has abundant reserves. In addition to natural bottom water reservoir, many fields have gradually approached to the bottom water reservoir development model in the secondary exploitation stage of oil.Horizontal well has the advantage of little produce pressure, large drainage area and can effectively suppress the rising water.So, it is widely used in bottom water reservoir development.However, there are still some problems to be solved in horizontal well development. For example,the huge difference between productivity formula predicting and actual value,the critical production calculation model is useless in oilfield production and both water cut increasing and production declining rule are difficult to grasp. Therefore,the article " Research on horizontal well productivity and reasonable parameters in bottom water reservoir ", to be carried out,has a extremely important significance on rational and efficient development of bottom water reservoir.Based on the above results of previous studies, a two-dimensional productivity formula and critical production model are established.And critical production model considering the impact of partition can be deduced by mirror reflection method. Production declining model and water drive characteristic curves are optimized and its associated solution model is built on the basis of the optimized results.This model can be used to predict water cut increasing and production declining rule. Water influx formula has been derived by using Welge equation and material balance principle.According to the above research, this paper mainly achieved the following understandings:(l)The horizontal well productivity model is built on existing research results.And the reliability of the proposed model is proved by example calculation.Then, Critical production model which are commonly used nowadays is analyzed.The research results show that diversity of the model and ignoring impact of partition are the major causes of leading to critical production which is difficult to guide field. Thus, an ideal formation and critical production model with a separator are presented.(2)The primary and secondary order of influence factors of production and critical production are studied by orthogonal experiment analysis.Importance of the production factors in turn are horizontal permeability, permeability anisotropy, horizontal length, the height of the horizontal section to avoid the water, producing pressure, reservoir thickness and oil viscosity while the critical production factors are horizontal permeability, permeability anisotropy, horizontal length, density difference between oil and water, avoiding water level segment height, reservoir thickness and oil viscosity.(3)Studies suggest that HCZ & D and HCZ & Zhang Jinqing type associated solution model are the best choices for forecasting well production declining and water-cut rising in bottom water reservoir.Besides, reasonable position of horizontal section should be 0.9h and optimal length of the horizontal section should be about 210m.(4)A computational model of water influx is established.Then, relationship between water influx and water-cut is studied. The results prove that oilfield water influx is increasing with the enlargement of moisture content. Water influx increases linearly with moisture content when water cut is less than 60% while formation deficiting lead to a sharp increase in water influx when water cut is more than 60% and its shape shows "upturned" growth when the water content is above 80%.