Study On Construction Parameters And Tools Of Hydraulic Blasting In Horizontal Wells

In recent years, horizontal wells are taken by domestic and foreign oil field as a main way to reduce production costs and improve the efficiency of oil and gas resources exploitation. In the producing process of a horizontal well of unconsolidated sandstone reservoir, sand is constantly moving into the wellbore. With production time increasing, the accumulated sand gradually formed a sand bed and led to decline in oil and gas production, even stopped production. It forced to conduct well repair and sand washing. At present, hydraulic sand washing as the main sand washing method is ensured by reasonable blasting critical flow rate and excellent washing tools, which are the key factors for safe and efficient horizontal sand washing operation. Therefore, it is significant to study on parameters of sand washing operation and tools used in hydraulic sand washing in the horizontal oil and gas well.Based on the studies at home and abroad, the following aspects had been done:(1) Overseas and domestic achievements and application situation of horizontal well hydraulic sand washing technology and tools were exhaustively investigated. On this basis, the problem that is difficult to calculate reasonable flow rate and lack of excellent hydraulic sand washing tools had been found. Therefore, this thesis did the research to solve the problems.(2) Fluid flow friction coefficient of horizontal well sand washing had been studied. Various factors affecting friction coefficient of sand flushing fluid flow and different calculation formula for calculating sand flushing fluid flow friction coefficient in different type of fluid, rheological model and flow state were collected and reorganized by analyzing the process of hydraulic sand washing process. Calculation model of frictional coefficient based on hydraulic sand washing in horizontal wells was established, which set up the theoretical foundation for calculation and analysis of operational parameter in horizontal well sand washing.(3) Study on establishment of solid migration model in the horizontal wells. After studying on the mechanism of horizontal well solid transport, analyzing of solid phase migration model in horizontal well at home and abroad and combining the horizontal well hydraulic sand washing operation, operation parameter calculation model of hydraulic sand washing in horizontal wells was established by introducing velocity distribution function and considering solid phase micro migration model of the horizontal well. It provides the theory basis for the hydraulic sand washing in horizontal wells.(4) Established the model of transient temperature field between stratum and well bore. The sand washing liquid viscosity is one of the important parameters of horizontal wells sand washing operation; however, no one considered the influence of transient temperature field to sand washing fluid viscosity. To solve this problem, this paper analyzed the physical process of stratum and wellbore heat transfer process and established the model of transient temperature field between stratum and well bore. By utilizing this model, change rules of sand critical flow rate influenced by stratum-wellbore temperature field were studied. This paper proved that considering transient temperature field of wellbore stratum is necessary in horizontal well hydraulic sand critical flow volumetric rate calculation in both qualitative and quantitative aspects.(5) Combining sand washing fluid friction coefficient calculation model and relationship between differential pressure and leakage volume, the effect of leakage stratum to the instantaneous temperature field was researched. The change regulation was found and relative calculation model and program were built. They provided a theoretical basis for the low pressure stratum of hydraulic sand washing operation.(6) Aiming at the problem that horizontal wells hydraulic sand washing tool cannot automatically adjust sand washing liquid jet direction. This paper designed a kind of self-adjustable horizontal wells hydraulic sand washing tool. This tool is designed to meet the high requirements of efficiency in different horizontal well hydraulic sand washing process by analyzing horizontal well hydraulic sand washing mechanism and characteristics. And then, this paper use FLUENT software to simulate nozzle layout and optimize nozzle layout, according to the theory of computational fluid dynamics.In a conclusion, this thesis made clear the mechanism of horizontal well hydraulic sand washing, found the factors that influence critical flow rate of the hydraulic sand washing in horizontal wells and designed a high efficiency of horizontal well hydraulic sand washing tool. All the researches provide basis and the method to improve the horizontal well sand cleanout efficiency and decrease accidents, which had important theoretical significance and practical value.