Abstract
Water invasion in carbonate gas reservoirs often results in excessive water production, which limits the economic life of gas wells. This is influenced by reservoir properties and production parameters, such as aquifer, fracture, permeability and production rate. In this study, seven full diameter core samples with dissolved pores and fractures were designed and an experimental system of water invasion in gas reservoirs with edge and bottom aquifers was established to simulate the process of water invasion. Then the effects of the related reservoir properties and production parameters were investigated. The results show that the edge and bottom aquifers supply the energy for gas reservoirs with dissolved pores, which delays the decline of bottom-hole pressure. The high water aquifer defers the decline of water invasion in the early stage while the big gas production rate accelerates water influx in gas reservoirs. The existence of fractures increases the discharge area of gas reservoirs and the small water influx can result in a substantial decline in recovery factor. With the increase of permeability, gas production rate has less influence on recovery factor. These results can provide insights into a better understanding of water invasion and the effects of reservoir properties and production parameters so as to optimize the production in carbonate gas reservoirs.
Highlights
The production of water from gas producing wells is a common occurrence in gas fields
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]
In the physical simulation of water invasion in gas reservoirs, previous studies only considered the elastic expansion of formation water when simulating the edge-and-bottom aquifer [20,21]
Summary
The production of water from gas producing wells is a common occurrence in gas fields. When the dynamic force at the wellbore exceeds the gravity force, the pressure gradient will cause the local gas-water contact to rise upward, which will contribute to water invasion and interfere with gas production. 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. The effects of the related reservoir properties and production parameters, such as water invasion energy, aquifer, production rate, permeability and fracture, were studied and discussed. These results can provide a better understanding of water invasion for improving the gas recovery and development benefit in carbonate gas reservoirs
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