Impact of Heterogeneity on Producing GOR for Tight Unconventional Wells
- Fahd Mohamad Alqahtani (Norwegian University of Science and Technology) | Abdul Saboor Khan (Norwegian University of Science and Technology) | Ellie Chuparova (Norwegian University of Science and Technology) | Curtis Hays Whitson (Norwegian University of Science and Technology)
- Document ID
- Society of Petroleum Engineers
- SPE Canada Unconventional Resources Conference, 29 September - 2 October, Virtual
- Publication Date
- Document Type
- Conference Paper
- 2020. Society of Petroleum Engineers
- 5.5 Reservoir Simulation, 3 Production and Well Operations, 2.4 Hydraulic Fracturing, 1.6 Drilling Operations, 2 Well completion, 5 Reservoir Desciption & Dynamics, 1.6.6 Directional Drilling
- fluid hetrogeneity, modeling, petrophysical hetrogeneity, producing GOR, unconventional
- 63 in the last 30 days
- 63 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 5.00|
|SPE Non-Member Price:||USD 28.00|
The purpose of this paper is to quantify the importance of lateral heterogeneity of permeability and porosity when modeling horizontal, multi-fractured tight unconventional wells exhibiting layer-wise fluid heterogeneity. Fluid and petrophysical properties are taken from the Eagle Ford basin.
A numerical simulation model of a horizontal well drainage volume with multiple planar fractures is created for two layers having distinct fluids (e.g. solution GORs). The model is populated with laterally-heterogeneous, correlated porosities and permeabilities (k=aφb) ranging from 4 to 14 %, and 59 to 2600 nd, respectively. The layer petrophysical properties can map differently for each layer, but the arithmetic average properties are equal for each layer. For all cases studied we assume the initial solution GOR to be areally homogeneous in a given layer; the solution GORs considered range from 1000 to 8000 scf/STB. The petrophysical heterogeneous cases are compared with homogeneous cases (no lateral property variation), both models with the same average petrophysical properties.
Results show that for a heterogeneous-petrophysical case with varying lateral contrast between the petrophysical properties in the two layers, individual fractures produce with distinct GORs, even showing a variation of producing GOR (Rp) from different locations within a single hydraulic fracture. However, the total, well-producing GOR behavior is very similar for the heterogeneous- and homogeneous-petrophysical cases, regardless of the fluid contrast in the two layers, when the maximum-to-minimum permeability ratio kmax/kmin<10.
These observations apply when flowing bottomhole pressure (BHP) is above (single-phase) or below (two-phase) in-situ saturation pressure. These results indicate that lateral petrophysical heterogeneity can often be ignored when modeling tight unconventional wells. The explanation for this non-intuitive result is that the producing surface area from many hydraulic fractures is so extensive that the well-average GOR is very close to the GOR of a well producing from two petrophysically-homogeneous layers having arithmetic-average porosity and permeability. This finding reduces considerably the simulation run time (CPU) using a single "average" hydraulic fracture element, where the key fluid heterogeneity is solution GOR in each layer.
Another important finding is that significant time-variation of producing well GOR may result even when flowing BHP remains higher than in-situ saturation pressures (i.e. single-phase flow). This behavior is caused by differential depletion of the individual layers with fluid contrast in viscosity and compressibility, i.e. without any contrast in layer permeabilities.
|File Size||1 MB||Number of Pages||28|
Zhang, M., & Ayala, L. F. 2015. Constant GOR as an Infinite Acting Effect in Reservoirs Producing Below (Dew/Bubble) Saturation Pressure. Paper presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas, USA, 28-30 September. SPE-175079-MS. https://doi.org/10.2118/175079-MS.
Aguilera, R. 2013. Flow Units: From Conventional to Tight Gas to Shale Gas to Tight Oil to Shale Oil Reservoirs. Paper presented at the SPE Western Regional & AAPG Pacific Section Meeting Joint Technical Conference, Monterey, California, USA, 19-25 April. SPE-165360-MS. https://doi.org/10.2118/165360-MS.
Behmanesh, H., Hamdi, H., & Clarkson, C. R. 2015. Analysis of Transient Linear Flow Associated with Hydraulically-Fractured Tight Oil Wells Exhibiting Multi-Phase Flow. Paper presented at the SPE Middle East Unconventional Resources Conference and Exhibition, Muscat, Oman, 26-28 January. SPE-172928-MS. https://doi.org/10.2118/172928-MS.
Cantisano, M. T., Restrepo, D. P., Cespedes, S., Toelke, J., Grader, A., Suhrer, M., & Walls, J. 2013. Relative Permeability in a Shale Formation in Colombia Using Digital Rock Physics. Paper presented at the Unconventional Resources Technology Conference, Denver, Colorado, USA, 12-14 August. URTEC-1562626-MS. https://doi.org/10.1190/urtec2013-092.
Coats Engineering 2019. www.coatsengineering.com (SENSOR).
Fetkovich, M. J., Bradley, M. D., Works, A. M., & Thrasher, T. S. 1990. Depletion Performance of Layered Reservoirs Without Crossflow. SPE Formation Evaluation 5 (3): 310–318. SPE-18266-PA. https://doi.org/10.2118/18266-PA.
McCoy, T. F., Reese, D. E., & Johnson, P. G. 2000. Depletion Performance of Poorly Stimulated Layered Reservoirs Without Crossflow. Paper presented at the SPE/CERI Gas Technology Symposium, Calgary, Alberta, Canada, 3-5-April. SPE-59757-MS. https://doi.org/10.2118/59757-MS.
Passey, Q. R., Bohacs, K., Esch, W. L., Klimentidis, R., & Sinha, S. 2010. From Oil-Prone Source Rock to Gas-Producing Shale Reservoir - Geologic and Petrophysical Characterization of Unconventional Shale Gas Reservoirs. Paper presented at the International Oil and Gas Conference and Exhibition, Beijing, China, 8-10 June. SPE-131350-MS. https://doi.org/10.2118/131350-MS.
Shepard, D. 1968. A two-dimensional interpolation function for irregularly-spaced data. Proceedings of the 23rd ACM National Conference, New York, 27-29 August, (pp.517–524). http://dx.doi.org/10.1145/800186.810616.
Tecplot 2019. www.tecplot.com (Tecplot RS).
Thrasher, T. S. 1995. Well Performance Monitoring: Case Histories. SPE Production & Facilities 10 (3): 177–183. SPE-26181-PA. https://doi.org/10.2118/26181-PA.
Van Laer, P., Leyrer, K., Povstyanova, M., Baig, M. Z., Makarychev, G., & Al-Marzooqi, H. 2019. Cenomanian Shilaif Unconventional Shale Oil Potential in Onshore Abu Dhabi, UAE. Paper presented at the Unconventional Resources Technology Conference, Denver, Colorado, USA, 22-24 July. URTEC-2019-526-MS. https://doi.org/10.15530/urtec-2019-526.
Whitson, C. H., Alqahtani, F. M., & Chuparova, E. 2018. Fluid Heterogeneity on a Well-Box Scale in Tight Unconventional Reservoirs. Paper presented at the Unconventional Resources Technology Conference, Houston, Texas, USA, 23-25 July. URTEC-2882502-MS. https://doi.org/10.15530/URTEC-2018-2882502.
Whitson, C. H., & Sunjerga, S. 2012. PVT in Liquid-Rich Shale Reservoirs. Paper presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8-10 October. SPE-155499-MS. https://doi.org/10.2118/155499-MS.