Horizontal Gas Well Stable Production Capacity And To Optimize The Design Study

Recently, due to the advantages of large producing area, high productivity of single well and production potential, horizontal well is becoming the main method of enhancing oil recovery in worldwide and it is necessary to study the reservoir engineering theory of horizontal well and hold the performance of horizontal well production. This paper focuses on the reservoir engineering, study deeply in the stable production ability of horizontal well through analytics method.So far, lots of research about exploring gas reservoir including theory of fluid flowing in well and well production ability analyse about horizontal well. Recently, horizontal well has been extensively used in gas reservoir exploitation, so it is very important and meaningful to explore the gas reservoir through the study of theoretical analysis method of horizontal wells stable production and the policy of the horizontal well exploitation.First of all, this paper studies the pressure drop computation theory of vertical section, inclined section, curved section in the horizontal gas well through traditional method, and then a detailed study of the horizontal wellbore pressure drop computation theory is carried out. When studying the theoretical calculation of horizontal well pressure drop, gas productivity index in the form of pressure square is first defined by imitating the definition of oil production index, also mathematical models of horizontal gas wellbore flow and gas reservoir seepage, which has the form of pressure square, are established. Then the production system analysis model under production coupling is built within the use of volume balance principle to connect the wellbore flow and gas reservoir seepage. Moreover, the expression that flow of the horizontal wellbore and pressure change with position is deduced, under three flow patterns:the laminar flow, smooth wall turbulent flow and rough wall turbulent flow. Based on natural gas flow mechanism in porous media, productivity analysis mathematical model of horizontal gas well is set up, and binomial production equation of horizontal well is obtained considering the formation damage and non-Darcy flow effect. By using the pressure drop analysis theory of horizontal gas wellbore and the binomial production equation, this paper gives the calculation method of formation pressure both in cases considering and regardless of wellbore pressure drop, and analyzes the stable production capacity of horizontal gas well. Finally, the geological factors which should be considered in the optimal design of horizontal gas well are discussed. And based on the horizontal wellbore pressure drop theory, the optimal length of the horizontal section is conducted, also according to the critical production and water breakthrough time, the best position of horizontal wells in gas reservoirs is discussed.In conclusion, through the study of theoretical analysis method of horizontal wells stable production, this paper provides a theoretical basis for optimizing horizontal wells design, determination of reasonable work system and gas production engineering.