The Characteristics Of Reservoirs And Stable Production Technology In Yan9of Hu151Well Area,Ordos Basin

Ordos basin, which is rich in oil and gas resources, is an important petroliferous basin in North China,However,there are difficulties in exploitation because of the low porosity and low permeability condition in reservoirs.Hu151block in An5oilfield is located in the Shanbei slope belt, Ding Bian city,Shanxi province.Because of the strong heterogeneity in the reservoir of this block, the oil production decline very quickly and there are have many difficulties in keeping oil production stable after several years of exploitation. Furthermore, it is difficult to adjust injection production and determine the reasonable water injection policy due to the uneven formation pressure distribution.The research focus of this paper is Yan9oil group in study area.Based on the well logging and core data and combined with the regional marker bed, the formation in the study area can be divided into two layers:Yan91and Yan92.Moreover,the sedimentary facies in the study area of this paper is identified as channel deposits according to the analysis of data.The types of the pore are mainly intergranular pore and feldspar dissolution pore,in reservoirs of study area. The pore throat types are mainly composed of necking and pore-shrinking. The reservoir has certain percolation ability due to the better pore structure. The main reservoir diagenesis types are compaction, pressolution and cementation. It has been obtained by analysis that the reservoir is in the stage A of late diagenesis.The decline in the production of oil wells can be analysed by the analysis of the productivity of the single wells,the initial productivity of the oil wells and controlling factors of productivity.Hu151well block has experienced a exploitation process from natural water drive to water flooding.The productivity in actual production process is lower than that in forecast of reservoir engineering. Initial productivity is controlled by the permeability and formation factor,and the decline in initial productivity was very small.After analysing the most of wells in the block,the change of production can be divided into three types:the rising daily fluid production, the stable daily fluid production, and the descending daily fluid production. Moreover,control measures have been put forward to study the corresponding type.After the rules of water-cut change has been summarized in study area, it is known that the initial water-cut is controlled by the oiliness of reservoir and the horizontal distribution of initial water-cut is controlled by reservoir structure.Hu151well block is greatly influenced by edge-bottom water,and there are two situations at present.The first is that the initial period of production is the high water cut period, and the production water is proved to be formation water. Wells in this situation with poor exploitation effect and plenty edge-bottom water,which are controlled by the level of the structure,are in the lower structure area in the west of reservoirs. The second case is the initial period of production of low water cut, and production water is proved to be formation water.Wells in the second situation with plenty edge-bottom water are in lower structure area in the west of reservoirs.The water content has rised and the exploitation effect has become poor due to the push of edge-bottom water.It had been found that injection water in the block has been gradually taken effect in2009with gradually rising formation pressure and uneven horizontal distribution of pressure field after analysing the energy utilization in Hu151well block.After analysing the water drive type in this block,it had been found that there are three water drive types in the block:elastic drive, injected water drive and edge-bottom water drive. It is known that the driving type has transferred from edge-bottom water drive to the injected water drive through the index of drive energy types in these years.The reasonable minimum flowing pressure can be deduced by the method of pump efficiency and the production experience in oil field. Thus the production pressure differentials can be obtained from that. The reasonable water injection of each single well and the reasonable water injection intensity can be figured out by the theoretical research of the intensity of water injection. Combined the fluid productivity intensity with the relation between water cut and rising rate of water cut in Hu151well block, the reasonable fluid productivity intensity can be analysed and the optimum injection-production ratio can be selected by scheme.Based on the adjustment of development management in active edge-bottom water area, the edge-bottom water can be prevented to push further through stronger control on the balance of injection-production. It is suggested to control fluid in the oil wells that have been water injected, and improve the utilization rate of water injection and net injection percent and promote the other oil wells to be effective in the water-injection area In the next step,it is suggested to put fluid-controlled into effects in order to prevent the breakthrough of the injected water that caused by high liquid-producing capacity.As to the injection policy,it is suggested to implement balanced injection to energize the formation and make foundation for stable production. Because the system of oil displacement by water has not been established well in the imbalance area of the surface of injection-production in well group,it is suggested to adopt unstable water injection.