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Journal of Petroleum Exploration and Production Technology

, Volume 6, Issue 4, pp 705–718

First Online: 01 February 2016Received: 09 October 2015Accepted: 13 December 2015

Abstract

This study analytically cross examines the consistency among available zero-dimensional material balance equations MBEs for liquid-rich gas equations and derive a new simple yet rigorous MBE starting from governing equations applicable to these systems. We propose a new zero-dimensional tank material balance equation directly applicable to the analysis of liquid-rich wet and retrograde gas reservoirs expressed as a function of an equivalent gas molar density, as well as investigate and critically compare its predictions against other zero-dimensional tank models proposed in the past for gas reservoir cases with different amounts of condensate content lean, intermediate and rich. All models are employed to predict reservoir performance given reservoir original-fluids-in-place and compared against benchmark examples created by numerical simulation. Actual field examples are also analyzed using existing and proposed models to test their ability to provide reliable reserve estimations using straight-line methods. The proposed density-based equation is proven to be straightforward to implement since it is written in terms of density, which allows it be directly expressed as an extension of the dry gas MBE, while not requiring the implementation of two-phase Z-factors.

KeywordsLiquid-rich Natural gas reservoirs Material balance equation List of symbolsBLReservoir hydrocarbon liquid phase formation volume factor, RB-STB

BVReservoir vapor phase formation volume factor, RB-SCF

Gfg,iInitial surface gas in reservoir vapor phase, SCF

GpCumulative gas production, SCF

GpTTotal cumulative gas production, including surface gas and gaseous equivalent of produced condensates, SCF

GiInitial gas-in-place, SCF

GTTotal initial gas-in-place, including surface gas and gaseous equivalent of produced condensates, SCF

NiInitial condensate-in-place, STB

NpCumulative oil production, STB

Nfo,iInitial surface oil in reservoir liquid phase, STB

niTotal initial hydrocarbon in place, lbmol

npTotal cumulative hydrocarbon production, lbmol

ngTotal moles of surface gas component at reservoir conditions, lbmol

ngpCumulative produced moles of surface gas component, lbmol

nopCumulative produced moles of surface oil component, lbmol

ngMoles of surface gas component in reservoir vapor phase, lbmol

ngMoles of surface gas component in reservoir liquid phase, lbmol

noMoles of surface oil component in reservoir vapor phase, lbmol

noMoles of surface oil component in reservoir liquid phase, lbmol

ΦPorosity

ρMolar density, lbmol-ft

ρVMolar density of reservoir vapor phase, lbmol-ft

ρLMolar density of reservoir liquid hydrocarbon phase, lbmol-RB

ρgscMolar density of surface gas at standard condition, lbmol-SCF

ρostMolar density of surface oil at stock-tank condition, lbmol-STB

ρgEquivalent gas molar density, lbmol-RB

\\overline{ ho } {g}^{*}\Equivalent gas molar density at average reservoir condition, lbmol-RB

pPressure, psia

pdewDewpoint pressure, psia

piInitial pressure, psia

tTime, day

TTemperature, F

kPermeability, md

hThickness, ft

reReservoir outer boundary, ft

rwWellbore radius, ft

RUniversal constant

RsSolution gas-oil-ratio, SCF-STB

RpsCumulative gas-oil-ratio, SCF-STB

RvVolatilized oil–gas-ratio, STB-SCF

fnLLiquid phase molar fraction at reservoir conditions, fraction

fnVVapor phase molar fraction at reservoir conditions, fraction

SVVapor phase saturation, %

SLLiquid phase saturation, %

qgscGas production rate at standard condition, SCF-D

qoscOil production rate at standard condition, STB-D

qVVapor production rate at reservoir condition, ft-D

qLLiquid production rate at reservoir condition, RB-D

RVRelative liquid dropout volume, fraction

v Velocity, ft-s

v V Velocity of reservoir vapor phase, ft-s

v L Velocity of reservoir liquid phase, ft-s

VbReservoir bulk volume, ft

VpReservoir pore volume, ft

VVReservoir vapor volume, ft

VLReservoir liquid volume, ft

ZtpTwo-phase compressibility factor

Ztp,CCETwo-phase compressibility factor from CCE experimental data

Ztp,CVDTwo-phase compressibility factor from CVD experimental data

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Autor: Miao Zhang - Luis F. Ayala

Fuente: https://link.springer.com/







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