Optimising Recovery in Gas Condensate Reservoirs

Abstract

Gas condensate reservoirs exhibit complex flow behavior below the dewpoint pressure, caused by compositional changes and the creation and growth of a condensate bank around the wellbore, which effectively reduces the relative permeability to gas flow. As a result, gas production decreases and liquid condensate, a valuable resource, is left behind in the reservoir.Well deliverability impairment resulting from liquid dropout has been a main focus of gas condensate studies for over 60 years. We have used compositional reservoir simulation, with representative lean-and rich-condensate fluids and velocity-dependent relative permeability models, to predict condensate dropout under typical operating conditions. The effectiveness of different production methods and remediation solutions in minimizing condensate buildup below the dewpoint pressure was quantified, using first a single-well model and then full-field models of tight and low-permeability gas condensate reservoirs in which six vertical wells were compared with two horizontal wells.We found that, although both horizontal wells and vertical well stimulation do improve well productivity, productivity enhancement depends greatly on well and reservoir parameters such as horizontal well lengths, well placement, reservoir permeabilities, and gas condensate compositions. For gas condensate production below the dewpoint pressure, it is possible to achieve an optimum balance between gas production rate and pressure drawdown, thus minimizing condensate dropout effect while producing at a reasonable rate. In a low-permeability gas condensate reservoir, the six vertical wells perform slightly better than the two horizontal wells for the same amount of gas production. In a tight gas condensate reservoir, on the contrary, gas recovery with two horizontal wells is significantly greater than with six vertical wells. Although, in this model, well stimulation can increase the productivity of the vertical wells in tight gas condensate reservoir, it is not as effective as using horizontal wells.

Investigation of the efficiency of gas condensate reservoirs waterflooding at different stages of development

“…Possible directions of condensate recovery dropped out from the gas in the formation are its transfer into the gas phase with subsequent extraction together with the gas, displacement from the porous medium by different working agents and their combination [2,3,12,[13][14][15]. The results of laboratory experiments on condensate displacement by water from models of porous media conducted in IFNTUNG were used in the design of further development of the Gadyach gas condensate field (horizon B-16) using intracontour (focal) flooding [7,16] and in the design of secondary condensate recovery from partial depleted gas condensate deposit of the horizon B-19b of the Anastasiyivske field [11,17].…”