Evaluation And Research Of Screw Pump Oil Recovery Technology On Heavy Oil Development

Haiwaihe and Xiaowa Oilfields that under the superintendence of Jinina Oilfield both have the problems of heavy oil and sand production. Some of the oil wells use screw pumps to produce oil, however, problems like rod breaking, pump stuck and incompatibility of pump discharge rate and fluid supply from oil wells occur often. The efficiency of various measures is only about 85%. Therefore it is important to conduct the application research on screw pump teclinology in order to improve the application effect and thus increase the benefit of the oilfield. The paper discussed the structural environment of the forming of the reservoirs and the reasons of sand production and the causes of heavy oil from the view points of geological features and petrophysical parameters of Haiwaihe and Xiaowa oilfields as well as the recovery technology of screw pump itself. The paper analyzed the structure of screw pump, its mechanism and special working conditions. With the effort of studying the screw pump recovery parameters and evaluating the field application of screw pump, major achievements were obtained. They are shown in the following aspects:1. Based upon the geological structural characteristics, reservoir and sedimentation characteristics and petrophysical parameters, the paper concludes that the reservoirs of Haiwaihe and Xiaowa oilfields are poor in diagenesis, high in shale content, unusual unconsolidation of reservoir structures and are likely to produce sands. High density, high viscosity and low wax content of in-situ oil are (he causes for heavy oil and intensive sand carrying capacity.2. Based upon the structure, working mechanism and characteristics of screw pump, the technical features for oil recovery of screw pumps are discussed: anti-sand stuck, suitable for heavy oil recovery, stable fluid production, advantageous for sand discharging and applicable to sand producing, heavy oil fields.3. Compared with the field empirical data of cold production of heavy oil in Canada, Haiwaihe and Xiaowa oilfields have unconsolidated reservoir, the oil itself has the capability of carrying sands. The oil density, reservoir thickness, porosity, permeability and oil viscosity are basically the same. It is concluded that these fields are fit for using screw pumps.4. The theory of screw pump recovery technology was put into practice and a thorough assessment was made upon the technical parameters of the screw pump. The technical parameters that suit Haiwaihe and Xiaowa Oilfields are determined. Tianjin made 120-36 screw pumps were chosen. The fluid supply capability of Haiwaihe oilfield was determined to be 10.13 m3/d , that of Xiaowa oilfield was 6.4m3/d with polished rod speed of 60-120 min-1 . Downhole string used 3"tubing and l'/8" D level sucker rod with the pump depth at 1000~l300m. The added light to heavy oil ratio for Xiaowa oilfield was decided to be 1:0.27. All these measures guaranteed the application result of screw pump at Haiwaihe and Xiaowa oilfields.5. The paper also discussed the problems of rod break-off, rod unscrewing and screw failure. Measures were undertaken, such as careful selection of rods, examination of the rods, application of anti-unscrewing device and special sucker rod just for the purpose of oil recovery. These measures were very effective for the prevention of rod break-off, rod unscrewing and screw failure and therefore ensured the efficient operation of oil wells.6. Through research and field application, it shows that screw pump oil recovery technology and its relevant technique have been developed to a mature degree. Statistics of 60 screw pumps used in the year 2001 showed that the success rate was 95%. Marvelous economic benefit was gained and the purpose of this research was achieved. The screw pump oil recovery technology of Haiwaihe and Xiaowa oilfields have reached international level and has the value of application more extensively.