Inflow Performance Relationships for Solution-Gas-Drive Slanted/Horizontal Wells

Abstract

SPE Member Abstract Since 1968, the Vogel equation has been used extensively and successfully for analyzing the inflow performance relationship (IPR) of flowing oil wells under solution-gas drive. Oil well productivity can be rapidly estimated by using the Vogel IPR curve and well outflow performance. However, the Vogel curve was originally developed for performance. However, the Vogel curve was originally developed for conventional vertical wells and may not be valid for slanted and horizontal wells. The development of IPR's for slanted and horizontal wells by using a vertical/horizontal/slanted well reservoir simulator is presented. Several important results were observed. First, the IPR's presented. Several important results were observed. First, the IPR's for slanted and horizontal wells are similar to the parabolic behavior of the Vogel IPR curve. Second, IPR data generated for slanted wells by using the Vogel curve can differ as much as 22% from that of the new IPR data and 27% for horizontal wells. Third, the right curvature shut of the Vogel curve for slanted and horizontal wells indicates that these wells are more efficient producers than vertical wells from a subsurface fluid flow viewpoint. Fourth, a minimum slant angle of 45 degrees is required to increase oil productivity by 50% over that of a vertical well. A slant angle of 60 degrees or greater can increase oil productivity more than two times that of a vertical well. The newly productivity more than two times that of a vertical well. The newly developed IPR data are compared with existing empirical and field data. Several application examples are presented to illustrate the use of these IPR's to predict slanted/horizontal well productivity. Introduction Oil well productivity (flow capacity) computation requires knowledge of the well inflow performance relationship (IPR). Simply stated, an IPR describes the relationship of well flowing bottomhole pressure (BHP) versus flow rate (q) at a stabilized reservoir pressure. pressure (BHP) versus flow rate (q) at a stabilized reservoir pressure. Several methods are available to prepare an IPR. Examples include the use of Darcy's equation, an empirical equation, and a reservoir simulator. For quick and accurate generation of an IPR curve, the use of the empirical Vogel equation developed in 1968 has been the most commonly used method in the oil industry. This equation analyzes the two-phase (oil and gas) IPR performance of a well producing from a reservoir under the solution gas drive mechanism. It was developed from a computer reservoir simulator solution to several solution gas drive reservoirs and for different fluid properties. (1) The Vogel equation is simple and is parabolic: In modern well nodal systems analysis of well productivity performance, the Vogel equation has become a standard tool for preparing performance, the Vogel equation has become a standard tool for preparing the IPR for a given well. Use of the Vogel equation is extremely simple. One set of stabilized well flow test data () suffices to generate the unique IPR for a given well. The obvious advantage of the Vogel equation is that h does riot require data for formation permeability, pay thickness, oil viscosity, and oil relative permeability. However, the Vogel equation was originally developed for permeability. However, the Vogel equation was originally developed for conventional vertical wells, and can generate erroneous IPR results for slanted (directional) or horizontal wells. Most off shore wells drilled and completed are directional. Numerous land wells in the Arctic and in other places such as man-made islands are also directionally drilled. With recent advances in drilling technology, many horizontal wells have been drilled and completed to boost oil and gas production from reservoirs that are riot economically productive when completed with conventional vertical wells. Likewise, horizontal wells have been drilled to produce oil in novel oil mining projects. Despite its inaccurate results, the Vogel equation has been extensively used to analyze the Productivity of directional wells. The generation of a Vogel-type IPR equation for a slanted (directional) well requires the use of a computer reservoir simulator that can analyze the flow behavior of such a well. Until recently, n o slanted well reservoir simulator had been reported. Its nonexistence may explain why no Vogel-type IPR equation for directional wells has been developed over the past two decades. Recently, NIPER developed a three-dimensional, three-phase reservoir simulator for analyzing vertical, horizontal, and slanted well that can be used to generate IPR equations for slanted and horizontal wells. In this simulator, a slanted/horizontal well model was developed to calculate the productivity index for each reservoir grid block penetrated by a productivity index for each reservoir grid block penetrated by a slanted/horizontal wellbore. The principal goal of this project was to develop IPR's for slanted or horizontal oil wells producing under the solution gas drive mechanism from homogeneous and isotropic reservoirs. Accurate IPR's for slanted/horizontal wells offer rapid and reliable well productivity results that can be used for making the important productivity results that can be used for making the important decision of whether to drill vertical, slanted, or horizontal wells in a given reservoir. LITERATURE REVIEW IPR's of horizontal and slanted wells can be generated using the productivity equations presented in references 4 through 8. productivity equations presented in references 4 through 8. P. 77