Abstract
Finding ways to accelerate the effective development of tight sandstone gas reservoirs holds great strategic importance in regard to the improvement of consumption pattern of world energy. The pores and throats of the tight sandstone gas reservoir are small with abundant interstitial materials. Moreover, the mechanism of gas flow is highly complex. This paper is based on the research of a typical tight sandstone gas reservoir in Changqing Oilfield. A strong stress sensitivity in tight sandstone gas reservoir is indicated by the results, and it would be strengthened with the water production; at the same time, a rise to start-up pressure gradient would be given by the water producing process. With the increase in driving pressure gradient, the relative permeability of water also increases gradually, while that of gas decreases instead. Following these results, a model of gas-water two-phase flow has been built, keeping stress sensitivity, start-up pressure gradient, and the change of relative permeability in consideration. It is illustrated by the results of calculations that there is a reduction in the duration of plateau production period and the gas recovery factor during this period if the stress sensitivity and start-up pressure gradient are considered. In contrast to the start-up pressure gradient, stress sensitivity holds a greater influence on gas well productivity.
Highlights
The large resource potential and reserve scale of tight sandstone gas reservoirs turn it into a significant strategic succession region regarding newly added proved gas reserves in China [1, 2]
In addition to the stress sensitivity which is necessarily considered in single gas flow, the existing water transformed the original single gas flow to gas-water two-phase flow in a tight sandstone gas reservoir [10, 11]; the relative permeability curves undergo changes with variation in the drawdown pressure [12, 13]
The existing water leads to mutual restriction between water and gas and later influences the gas flow to be affected by the start-up pressure gradient [14, 15]
Summary
The large resource potential and reserve scale of tight sandstone gas reservoirs turn it into a significant strategic succession region regarding newly added proved gas reserves in China [1, 2]. There always exists some associated water in it, due to the particularity of tight sandstone gas reservoir. It increases the reservoir water saturation because of the invasion of fracturing fluids. The existing water increases the complexity of the flow mechanism in a tight sandstone gas reservoir [8, 9] and results in its radical transformation. In addition to the stress sensitivity which is necessarily considered in single gas flow, the existing water transformed the original single gas flow to gas-water two-phase flow in a tight sandstone gas reservoir [10, 11]; the relative permeability curves undergo changes with variation in the drawdown pressure [12, 13]. Water produced in tight sandstone gas reservoir has largely impacted productivity. An in-depth analysis must be given to the effect of water on tight sandstone gas reservoir development in order to decide the primary impacts of productivity of tight sandstone gas reservoir with water produced, providing theoretical support for improvement of tight sandstone gas reservoir development
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call