The thesis takes inspiration from the idea presented by Whitson et al. (2018) to investigate the impact of fluid and rock heterogeneity in a single well drainage volume in an unconventional shale reservoir. Literature study shows that significant spatial variation exists in producing GOR from wells in unconventional plays and indicates the possibility of fluid variation at a well-box scale. However, little work has been done to study the effect of fluid heterogeneities in a single horizontal well drainage volume.
The study involves porosities that range from 2% to 20%, while permeability that ranges from 5 nD to around 3000 nD. Fluid is kept constant in the areal direction but is varied with depth, ranging from 1000 scf/stb to 10000 scf/stb. Producing GOR is calculated for both undersaturated and saturated reservoir conditions from a model with two layers with distinct fluids.
The study encompasses derivation of an analytical equation to calculate initial producing GOR of a two-layered, heterogenous-fluid shale well by making use of transient linear flow equation. This analytical equation is then utilized to quickly calculate the initial producing GOR of a two-layered heterogenous-fluid shale well without the use of numerical simulation. This approach can be used to initialize and history match fluids in shale wells where fluids in individual layers are not known.
The results are matched with results from a numerical simulation model. The program gives results with high level of accuracy for undersaturated conditions with error not exceeding 2% for the different cases considered. However, for saturated reservoir conditions, the error becomes large and the results are not sufficiently accurate. Similarly, the program also outputs multiple combinations of layer solution GOR that can result in a defined target well producing GOR.