Impact of reservoir and well parameters to the production performance of horizonal well in gas and gas condensate reservoir.
Zulkipli, Siti N. F.
Engineering Honours Degree 2008
University of Adelaide
Application of horizontal well in field development has gained much attention in the industry since 1990s especially in oil reservoir. Some of the advantages offered by horizontal well include larger drainage area, minimize drawdown and non-Darcy flow effect, delay water break-through and condensate bank formation and increase in productivity to name a few. Despite its wide application, however, not much study has been conducted about horizontal well operation in gas and gas condensate reservoir. This report presents this gap and highlights various reservoir and well parameters that may affect gas production from horizontal well. These parameters include permeability, porosity, reservoir and bottom hole pressure, drainage and well-bore radius, well length, thickness, completion types, skin factor, turbulence flow, condensate drop-out, water coning and liquid hold-up to name a few.
Methodology involved in this study includes IPR curve analysis and ECLIPSE 300 simulation. Outflow performance of horizontal well and comparison between horizontal well and vertical well performance are also investigated.
Based on the study, anisotropy ratio, fracture dimension, porosity, pressure, permeability and thickness have the greatest impact in improving gas production while liquid hold-up, condensate build-up, water coning and variable skin due to various completion types have the most influence in reducing gas recovery from horizontal well. Other factors such as turbulence, drainage and well-bore radius do not have much effect on the gas recovery. For outflow performance, reasonable rates are achieved considering friction effect. Sensitivity run of tubing size indicates higher gas rate is obtained for larger tubing diameter. Compared to vertical well, horizontal well gives much better production in both turbulent and non-turbulent flow condition. Results from multi-variable sensitivity analysis prove to be more realistic and reliable compared to single-variable sensitivity analysis.
Some techniques to prevent condensate build-up may include dry gas cycling to maintain high reservoir pressure and maintaining wellbore pressure to be above the dew point. Other ways to mitigate this problem include use of chemicals to dissolve the condensate, use of surfactant to reduce the interfacial tension of the condensate and increasing flow rate to reduce condensate accumulation near the well-bore region. On the other hand, water breakthrough can be delayed either by application of inflow control device to create a more uniform pressure and influx profile or completing the well as far as possible from the gas water contact level. For liquid hold-up, the best way to mitigate it is by increasing flow rate and maintaining high well-bore pressure while for sand control, optimum completion design such as liner and gravel packing needs to be employed to reduce skin factor as well.
In conclusion, all the reservoir and well parameters that may affect gas production from horizontal well need to be optimized and investigated through detailed analysis to maximize gas recovery with minimum production and intervention cost.