Estimation of 3D Distribution of Pore Pressure from Surface Drilling Data - Application to Optimal Drilling and Frac Hit Prevention in the Eagle Ford
- James Kalinec (Equinor) | Mohit Paryani (FracGeo) | Ahmed Ouenes (FracGeo)
- Document ID
- Unconventional Resources Technology Conference
- SPE/AAPG/SEG Unconventional Resources Technology Conference, 22-24 July, Denver, Colorado, USA
- Publication Date
- Document Type
- Conference Paper
- 2019. Unconventional Resources Technology Conference
- 11 in the last 30 days
- 161 since 2007
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The proper 3D estimation of pore pressure is a critical factor for a successful development of shale reservoirs where the optimal drilling and fracing requires the constant knowledge of this reservoir property. Unfortunately, classical pore estimation methods require wireline logs that are not widely available in shale plays and the common industry methods are not adapted to resource plays. The new workflow illustrated in this study uses surface drilling data combined with the Corrected Mechanical Specific Energy (CMSE) to estimate the pore pressure at any well in real time during drilling. Since the surface drilling data are available at all the past, and currently drilled wells, the estimated pore pressure logs can be propagated in 3D and used to optimize the drilling and fracing of the unconventional wells. Most importantly, the ability of the new approach to detect low pore pressure zones, provides a practical diagnosis tool to detect potential interference zones due to depletion of parent wells.
The availability of standard surface drilling measurements such a weight on bit, ROP, RPM and Torque provides the unique opportunity to estimate the Mechanical Specific Energy (MSE). Unfortunately, the MSE computed at the surface is not representative of the downhole MSE which could be derived after applying the proper friction loss correction. This field-tested approach was validated with DFIT in many wells and provides a real time estimation of the pore pressure log along the lateral section of the unconventional well. Once the pore pressure logs are estimated in past wells and current ones, a 3D distribution can be derived by using geostatistics and/or neural networks. The 3D model of pore pressure could be used during the drilling of new wells but also during the stimulation where abnormally low pore pressure zones could be a strong indication of depletion from parent wells. With this new knowledge at hand, the selection of the frac stage positions could be optimized to avoid such low pore pressure zones that could cause frac hits.
The new workflow is validated with multiple wells from South Texas where wireline logs and DFIT data confirmed the presence of large variations of pore pressure values including potential zones that could be responsible for frac hits. The validation confirmed that with the CMSE and its friction loss correction, the use of surface drilling data as a source of pore pressure information is practical and cost effective. Distributing the derived pore pressure logs in 3D creates the unique opportunity to update the 3D distribution of pore pressure after the drilling of each new well.
For faster drilling and for preventing fracing into depleted zones, the resulting 3D pore pressure distribution derived solely from the surface drilling data adds significant value to the shale plays without costing more. Interdisciplinary components of drilling and reservoir engineering are integrated together with geomechanics to address the important issues of pore pressure estimation.
|File Size||572 KB||Number of Pages||12|