Well Deliverability Predictions for a Low-Permeability Gas/Condensate Reservoir

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIt is well known that the deliverability of gas condensate wells can be impaired by the formation of a condensate bank once the bottomhole pressure drops below the dew-point. There have been many excellent laboratory studies on gascondensate relative permeability that describe this phenomenon, but integrated laboratory-simulation-field studies that compare systematic predictions to field performance are few. This work presents a careful and comprehensive evaluation of deliverability of several wells in a low permeability gas condensate reservoir. This sandstone reservoir has permeability ~ 10 md, porosity ~ 10%, and condensate yield ~ 50 bbls/MMscf.Our approach consists of the following steps -(i) careful selection of core samples that cover the range of expected responses; (ii) design of fluid systems that mimic reservoir fluids, but at lower temperatures; (iii) appropriate relative permeability measurements k rg = f(k rg /k ro , N c ) for a range of flow conditions; (iv) fitting this data to several different relative permeability models for use in reservoir simulators;(v) use of analytical spreadsheet tools to calculate deliverability; (vi) detailed single well compositional models with realistic geology and boundary conditions extracted from full field models, honoring complex producing rules and differential depletion; (vii) comparison of prediction to four wells, three vertical and one inclined.We have been able to reasonably predict the performance of these wells. The productivity reduction of the wells were found to be in the range of 80%, the majority of which occurred in the initial phases of production. Our ability to reasonably predict the performance has given us confidence that our approach, including measuring only the relevant portion of the relative permeability curves and using synthetic fluids, may be sufficient.

Mobility ratio, relative permeability and sweep efficiency of supercritical CO2 and methane injection to enhance natural gas and condensate recovery: Coreflooding experimentation

“…Capillary forces often render the condensate immobile and that these microscopic liquid droplets tend to be trapped in small pores or pore throats. This near-well chocking can reduce the productivity of a well by a factor of two to four (Afidick et al, 1994;Barnum et al, 1995;Smits et al, 2001;Ayyalasomayajula et al, 2005). The severity of this decline is to a large extent related to fluid phase behaviour, flow regime (Darcy or non-Darcy), interfacial forces between fluids, capillary number, basic rock and fluid properties, wettability, gravitational forces as well as well type (well inclination, fractured or non-fractured).…”

Assessment of the recovery and front contrast of CO2 EOR and sequestration in a new gas condensate reservoir by compositional simulation and seismic modeling

“…This liquid zone around the gas well is called the ''condensate bank.'' Condensate banking can reduce well productivity significantly by 50-80% [5]. The monitoring of condensate banking could be done by regular pressure transient test or by formation tester tools [3,4].The formation tester tool may be limited due to its small radius of investigation.…”

Chemical Stimulation of Gas/Condensate Reservoirs

“…1 The degree of condensate blocking depends on a combination of factors including fluid properties, formation characteristics, flow rate and pressure. [2][3][4][5][6] Since the reduction in well productivity is primarily associated with the reduction in gas relative permeability, a great deal of effort has gone into measuring and modeling the relative permeability of gas-condensate fluids. Several recent studies have been made using the pseudo pressure or flash method for measuring steady state gas and condensate relative permeability.…”

“…Several recent studies have been made using the pseudo pressure or flash method for measuring steady state gas and condensate relative permeability. [2][3][4][5][6][7][8][9][10][11][12][13] In this method, a gas mixture above its dew point pressure is flashed into the core at a reservoir pressure less than the dew point pressure and flowed until steady state is reached.…”

“…14 Later studies were done at reservoir conditions with synthetic fluids 4,6,7 as well as with reservoir fluids. 15 Various parameters such as interfacial tension, 16 high flow rates, 17,18 non-Darcy effects, 19 fluid composition 16,20 and rock type 5,20,21 have been investigated.…”