Gas Drilling Cuttings Bed Movement Of Particles Distribution And Destruction Method

Gas drilling is a low pressure under-balanced drilling technology with circulating medium of air or other gas, has incomparable advantages than conventional mud drilling, which provides a revolutionary treatment for oil and gas exploration and development of China’s large area low porosity, low permeability, low pressure, low abundance and solving the technical problems of drilling engineering and largely enhancing the drilling speed and avoiding or controlling the vicious lost circulation. However, in the gas drilling practice, cuttings particles easily settle down into cuttings bed because of the characteristics of small gas buoyancy, low density, poor viscosity, and the exist of cuttings bed will increase the drilling torque and friction which directly affects the service life of drill pipe and the safety of drilling. In addition, the drilling pressure applied and putting down logging instrument will also be affected which reduces the success rate of operation.Aiming at the problem of carrying cuttings in gas drilling, accesses to the domestic and foreign research present situation of cuttings transportation and motion distribution of cuttings bed in gas drilling and surveys the potential hazards of cuttings bed, this paper uses combining methods of theory analysis and numerical calculation to study cuttings transportation and motion distribution of cuttings bed in gas drilling, and puts forward the cuttings bed destruction tool used in gas drilling to prevent and destruct cuttings bed including its rational structure parameters advice.The main research work are as follows:(1) Conducting the mechanical analysis of the gas drilling immobile particles of cutting bed in deviated and horizontal section to theoretical calculate the influence parameters of restarting conditions of immobile particles of cutting bed.(2) Establishing the gas drilling "drill pipe-borehole" three-dimensional finite element simulation model, and conducting by CFD transient simulation technology for numerical simulation of gas-solid two-phase flow to obtain the motion distribution law of cuttings bed particles in small, medium and large deviated wells and the influence of operating parameters such as gas velocity, gas viscosity, particle diameter, rotation speed of drill pipe and eccentricity of drill pipe on the motion distribution law of cuttings bed particles.(3) Referring to the structure features of cuttings bed destruction tool used in mud drilling, this paper designs the structure of cuttings bed destruction tool used in gas drilling and establishes three-dimensional finite element simulation model to analyze the working characteristics and structure parameters sensitivity of the tool by CFD and CAE simulation technology.(4) Establishing the gas drilling "cuttings bed destruction tool used in gas drilling-drill pipe-borehole" three-dimensional finite element simulation model, the feasibility and effective distance of the tool are studied by CFD transient simulation technology.(5) Based on the analysis of gas-solid two-phase flow law and structure parameters sensitivity of the tool, this paper completes the job of processing drawing of cuttings bed destruction tool used in gas drilling.The research work of this paper is conducive to scientifically realize the cuttings transport properties in gas drilling and reveal the motion distribution law of cuttings bed particles in gas drilling, and the conclusion can be used to obtain guide for site construction. The cuttings bed destruction method proposed can effectively improve the cuttings transport efficiency to solve the unfavorable effect of the problem of cuttings bed on drilling operation in gas drilling.