2017_EJRNL_PP_XIAOLIANG_HUANG_1.pdf
Terbatas  Suharsiyah
» Gedung UPT Perpustakaan
Terbatas  Suharsiyah
» Gedung UPT Perpustakaan
The production process in the gas reservoir with an aquifer is complex. With gas production, aquifer
water could possibly flow into the production well and accumulate within the well bore, which leads to a
lower production rate and may even block the producer. However, few studies in the literature investigate the damage caused by the liquid phase in this kind of reservoir or predict gas productivity using
the relationship between reservoir pressure and water gas ratio (WGR). For this reason, it is important to
know the effects of the formation of liquid phase behavior on production when an aquifer is present
under a gas reservoir.
From the results of published literature reviews, we found that studies focused on the production of a
gas reservoir with bottom water. Nevertheless, for gas well damage from the liquid phase behavior, we
found that there was no statistical data or mathematical model of the relationship between reservoir
pressure and the gas oil ratio (GOR), which affects production.
In this research, based on the theory of fluid flow in porous media, a new mathematical model of water
and gas production and a new equation on gas well productivity is developed. To verify the model and
equation, gas production data collected from the field are applied. By analyzing the typical gas reservoir
with bottom water and the collected data, influences from the liquid phase behavior are shown. In this
way, mathematical relationships between reservoir pressure and the WGR and between the GOR and
production decline were obtained. The new gas productivity model is derived from the gas and water
pseudo pressure functions, which can be applied to analyze well damage caused by the liquid phase.
In order to verify the mathematical model, production data were collected from a typical gas reservoir
with an aquifer located in the Changxing gas reservoir. The results indicate that a semi-logarithmic linear
relationship is obtained between the WGR and productivity decrease. When the WGR increases from 0.5
to 15 m3
/104 m3
, damage caused by liquid phase decreases to 59%.
The tendency of gas productivity in the Changxing gas reservoir was obtained so that it decreases as
reservoir pressure decreases and increases as the WGR decreases. The gradient of the gas productivity
deduction increases as the WGR increases. By the end of the data analysis, two linear equations indicating the relationship between gas productivity and reservoir pressure and the relationship between
gas productivity and the water gas ratio are obtained: QAOF ¼ A1lnWGR B1 and QAOF ¼ A2lnP B2,
respectively.