Optimising Spacing of Horizontal Wells in Gas and Gas-Condensate Reservoirs

Abstract

An increase in the demand for gas in this current generation and the availability of several technologies including horizontal drilling technology has opened up the development of tight gas reservoirs throughout the globe. Efficiently draining the reservoir using hydraulic fracturing strongly depends on well spacing, especially for low permeability reservoirs. Most of the majority of work done by petroleum industries in the world especially in the Russian Federation to find the optimum well spacing is based on economic and technical considerations. Key factors influencing performance of gas and gas condensate reservoirs include controllable and uncontrollable factors. Uncontrollable factors include porosity, water saturation, net-to-gross, initial pressure, permeability, natural fractures and fluid properties. The most relevant parameters among the controllable factors to consider for optimizing well spacing in gas and gas condensate wells are well design variations, well placement, surface facilities design, completion technologies and operating conditions which also include parameters such as the reservoir thickness, permeability anisotropy ratio, fracture conductivity, induced fractures and fracture half-lengths. Due to the dearth of interference test data in gas wells and the inaccuracy of analytical solutions, numerical simulation is the most suitable approach for optimizing spacing in gas wells. In finding the optimum well spacing, several simulation runs are carried out for a real range of well and reservoir variables. The results are then tabulated and translated into a 15 and 45-year cumulative production as a function of well spacing, with the results indicating that lower permeability reservoirs require closer well spacing. In the case of a large number of long fractures, wells need to be placed further away from each to reduce well interference. This paper outlines the outcomes of optimization studies on well spacing in which both analytical and numerical tools were used in the presented workflow for several development scenarios in the gas and gas-condensate reservoir environments.