Intelligent Dynamic Production Allocation for Commingled-Producing Wells in High-Contrast Reservoirs

Abstract

Abstract Production allocation for wells producing from multiple reservoirs is a widely-existing challenge, especially for reservoirs with high-contract properties. Traditional methods of allocation may not provide reliable contribution of reservoirs and do not capture the dynamic change of reservoir and well conditions. Production-logging-tool measurement is usually utilized to allocate production for reservoirs, but it only reveals the production contribution at a certain time under an operating condition. The commonly-used KH (permeability by net-pay) method fails to capture reservoirs of high-contrast pressure and fluid properties. It is imperative to establish a robust method to determine the contribution of oil-gas-water for commingled wells. An integrated approach of production allocation has been proposed in an efficient manner to calculate allocation factors. Firstly, the wells producing from multiple reservoirs are clearly identified in each period based on perforation/completion history and well tops. The open-hole-log interpretation for permeability and net-pay is extracted for each perforated reservoir. Secondly, pressure contrast between reservoirs has been acquired, giving pressure gradient. The dynamic change of reservoir pressure is also derived from the historical pressure measurement. Thirdly, the producing wells usually have routine tubing-head-pressure, from which the bottom-hole-flowing pressure is automatically computed from vertical-flow-performance (VFP) table on a daily/monthly basis, depending on the lift-type of natural flow or artificial lift. The pressure difference from each reservoir to bottom-hole is then quantified. In addition, each reservoir fluid property is extracted from PVT-database. Therefore, allocation factors of oil-gas-water are proportionally allocated based on the weights of permeability-net pay by pressure-difference over viscosity. The change of perforation history is also considered; accordingly, allocation factors are updated. PLT data if available are used to consolidate the weight of allocations. Albeit high-contrast reservoirs together with complex perforation events, the methodology of intelligent production allocation has been systematically utilized for commingled-producing wells in an automatic and efficient manner. Multiple wells are accurately quantified in production contribution. It reduces the manual time from several months to days. The allocation results match PLT and represent the real reservoir conditions, giving dynamic reliable reservoir contribution. Some wells producing in late stage may pose excessive gas/water production from certain reservoirs, which are considered based on PLT and well surveillance, to help tune the allocations. The accurate production is fed into dynamic simulation for the improvement of history match on the well and commingled reservoirs, and development strategy. This approach represents a novel and innovative means of integrating fluid properties, petrophysics, well history, wellbore modelling for robust production allocation. The process of allocation factor is performed automatically for each well producing from multiple reservoirs, and extensible to a single reservoir with multiple sub-reservoirs to understand the different level of depletion using artificial intelligence.