Evaluation of water coning phenomenon in naturally fractured oil reservoirs

Abstract

Water coning is a complex phenomenon observed in conventional and unconventional reservoirs. This phenomenon takes place due to the imbalance between viscous and gravitational forces during simultaneous production of oil and water. In a fractured reservoir, controlling of water coning is challenging due to the complexity originates from large number of uncertain variables associated with such reservoirs system. This paper presents a fully coupled poroelastic multiphase fluidflow numerical model to provide a new insight and understanding of water coning phenomenon in naturally fractured reservoir under effect of various rock and fluid properties. These properties include anisotropy ratio, fracture permeability, mobility ratio, and production rate. The simulation workflow of the developed numerical model is based on upstream flux weighted finite element discretization method and a new hybrid methodology, which combines single-continuum and discrete fracture approach. Moreover, the capillary pressure effect is included during the discretization of the partial differential equations of multiphase fluid flow. The numerical system is decoupled using implicit pressure and explicit saturation (IMPES) approach. Discretization of water saturation equation using standard finite element method produces solution with spatial oscillations due to its hyperbolic nature. To overcome this, Galerkin's least square technique (GLS) is employed to stabilize the equation solutions. The developed numerical scheme is validated successfully against Eclipse-100 and then applied to a case study of fractured reservoir taken from Southern Vietnam. The results showed that the break through time is very sensitive to the distributions of fracture network, anisotropy ratio between fracture horizontal, vertical permeability, and mobility ratio. Furthermore, it has been concluded that aquifer strength has a little effect on coning behavior during oil production process.

Controlling excess water production in fractured carbonate reservoirs: chemical zonal protection design

“…Fang et al (2017) addressed a similar problem for a gas reservoir. Their observation differs from that of Reda is that, whereas Reda (2016) claims that oil reservoir aquifer strength has a little effect on produced water cut, Fang et al (2017) found great impact of aquifer size and strength on gas productivity and water cut, possibly because of higher dissolved gas in water.…”

“…Inamullah et al (2015) have shown through simulation that optimum oil production rate is to be reduced to half of that of maximum production rate if the coning effect is to be minimized. Controlling water coning in fractured reservoirs is more challenging than the homogeneous reservoirs because of the rapid movement of water through the fractures (Reda 2016). To counter the problem, Dabiri et al (2017) suggested the benefits of horizontal wells over vertical wells, showing (through simulation) that critical oil production rate in horizontal wells is greater than that of vertical wells in fractured formations.…”

Water Intrusion Characterization in Naturally Fractured Gas Reservoir Based on Spatial DFN Connectivity Analysis

“…In a fractured reservoir, controlling water intrusion is challenging due to the complexity that originates from a large number of uncertain variables associated with the representativity of the natural fractures' attributes and spatial distributions. These water intrusion occurrences have been observed and evaluated for a long time by many studies [4][5][6][7][8][9]. Sheng et al [4] present a parametric study that analyses the effect of matrix and fracture permeability, well penetration, vertical anisotropy, aquifer size and gas rate production on water intrusion.…”

Experimental Study on the Physical Simulation of Water Invasion in Carbonate Gas Reservoirs

“…Water invasion is a complex phenomenon observed in oil and gas reservoirs, which will occur due to pressure gradients close to the production well and the imbalance between the viscous and gravity forces around the completion interval [7,8]. There are three essential forces controlling the mechanism, which includes the capillary, viscous and gravity forces [6].…”

“…Hu et al [20] and Shen et al [21] used reservoir cores to analyze the effects of different aquifers on water invasion. Azim [7] proposed a fully coupled poroelastic multiphase fluidflow numerical model to understand the water coning phenomenon in naturally fractured reservoir under the effects of various rock and fluid properties. So far there has been a lot of research work carried out on the performance of water invasion in gas reservoirs.…”