The Theoretic Study Of Productivity Of Horizontal Well

At present, the technique of horizontal well has become an important measure for the development of new fields, enhancing old well productivity and improving the recovery ratio, which is increasingly important in oil field development. Recently a great deal of studies about horizontal well have been done, but the theory of productivity prediction is not mature, which is the restrictive factor to a certain degree.In this thesis, the methods of productivity prediction of horizontal well are studied by applying the seepage flow theory, reservoir engineering theory, oil-gas field development, complex variables functions and so on. Research results are as follows:1.Base on the ellipsoidal flow pattern of horizontal well, the seepage flow theory of isobaric ellipsoidal surface is analyzed and studied. A new productivity formula of conventional horizontal well is derived, and the influencing factors are analyzed in this thesis, which provides a preference for the conventional horizontal well productivity prediction.2.The seepage flow theory of multi-lateral wells is systematically studied in this thesis. Based on the conformal mapping theory, method of mirror and equivalent flow resistance method, a new productivity formula of multi-lateral wells is derived, which provides a preference for the multi-lateral wells productivity prediction. Many influencing factors are analyzed, such as the length of horizontal well, number of lateral hole, formation thickness, permeability anisotropy of reservoir, well placement and so on.3.The seepage flow theory of horizontal well pattern is studied in this thesis. Based on the method of pseudo three-dimensional and theory of equivalent flow resistance, productivity formulas are derived about horizontal well pattern, including 5-spot pattern, 7-spot pattern and 9-spot pattern. This thesis provides a preference for the horizontal well pattern productivity prediction. Many influencing factors are analyzed, such as the length of horizontal well, direction angle of horizontal well, formation thickness and so on.4.On the basis of the complex potential theory and potential superposition principle, a new seepage flow model for productivity prediction of horizontal well after hydraulic fracturing is derived, which provides a preference for horizontal well after hydraulic fracturing. Many influencing factors are analyzed, such as fracture location, fracture length, fracture interval, fracture flow capacity and so on.5.A mathematic model of seepage flow in the productivity section coupling reservoir flow and variable mass pipe flow of stepped horizontal well is derived through the potential superposition theory and the theory of infinitesimal line congruence. 6.The ellipsoidal flow pattern of horizontal well is a isotonic ellipsoidal surface on the plane and a isotonic rotating ellipsoidal surface in three dimensional space. On this basis a three-dimensional mathematical model of oil-water two-phase seepage flow of horizontal well is derived. The water saturation distribution is derived and the law of the moving boundary is found. The formulae of indices calculation, including oil productivity, differential pressure and water breakthrough time are derived, which provides a basis for the practical application of development technique of horizontal well.This thesis improves the theory of productivity prediction of horizontal well, which offers a foundation for horizontal well design and productivity analysis.