Inflow Performance Relationships for Solution-Gas-Drive Reservoirs

Abstract

In this theoretical study, a numerical model was used to examine the influence of pressure level and skin factor on the Inflow Performance Relationship (IPR) of wells producing solution gas drive systems. Examination of the synthetic deliverability curves suggests that the exponent of the deliverability curve is a function of time, and that the exponent is usually greater than unity. The implication of this observation to field data is discussed. The accuracy of procedures given in the literature to ~redict oil-well deliverabilities is also examined. It is shown that the methods given in the literature can be used to predict future performance provided that the exponent of the deliverability curve is known and extrapolations over large time ranges are avoided. If single point tests are used to predict future performance (such tests assume that the exponent of the deliverability curve is constant), then errors in predictions will be minimized if test conditions correspond closely to actual producing conditions. Under these circumstances errors in rate predictions will be directly influenced by the magnitude of the error that results in assuming 199 that the exponent of the deliverability curve is known.Although, relative permeability and fluid property data are required, the Muskat mat~rials balance equation and the assumption that gas-oil ratio is independent of distance can be used to predict future production rates. This method avoids problems associated with other methods in the literature and always yields reliable results.New methods to modify the IPR curve to incorporate changes in skin factor are presented. A new definition of flow efficiency that is based on the structure of the deliverability equations for solution gas drive reservoirs is proposed. This definition avoids problems that result when the presently available methods are applied to heavily stimulated wells.

Modeling Inflow Performance Relationship for Three Phase Flow in Bounded Reservoirs.

“…In addition, as the value of skin-factor becomes negative, Standing approach creates physically inadequate outcomes (the oil flow rate decrease at the low values of bottomhole pressure). As later proven by Camacho et al 6 and Wiggins 7 the shape of IPR curve was not affected by the existence of skin-factor. The outcomes achieved by Standing are correlated to the skin-factor as a non-dimensional pressure alteration nearby the wellbore which is linearly rely on the oil flow rate.…”

Decline Curve Analysis for Multiphase Flow.

“…Using this equivalent liquid rate in dimensionless rate or pressure means that the constant 141.2 has to be changed to 25. 16 From Appendix A, we find that Eq. 19 can be derived in terms of equivalent liquid variables for a radial reservoir as shown Eq.…”

“…1 for solution-gas drive reservoirs for two-phase flow of oil and gas under boundary dominated flow conditions where oil is the dominate flowing phase. [16][17][18][19] Ther showed the gas-oil ratio is uniform between the wellbore and the location of the average reservoir pressure after the two phase zone had moved pass the location of average reservoir pressure. They found that the Muskat material balance equation could be used to predict the volumetrically averaged saturations versus average reservoir pressure.…”

Boundary-Dominated Flow in Solutions-Gas-Drive Reservoirs

“…In Ref. 19 we noted that on the basis of an examination of inflow performance relations, non-Darcy flow may be the norm in solution-gas-drive reservoirs. On the basis of observations given here, it appears that non-Darcy flow may yield a constant value of b.…”