Determining Fracture Pressure Gradients from Well Logs
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2020-02-18 https://doi.org/10.14419/ijag.v8i1.29162
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Fracture gradient, Overburden stress, Pore Pressure, Poison’s Ratio. -
Abstract
Fracture pressure gradient is one of the essential parameters used in determining mud weight profiles during drilling operations. We have determined fracture pressure gradients from well logs obtained from three producing wells in Onshore Niger Delta using an empirical model. Key logs needed for the prediction were conditioned and quality controlled to meet the standard required for reliable results. The true vertical stress, normal compaction trend and compressional shale velocity trends were generated from the logs (density and sonic logs). Poison’s ratio was obtained from compressional and shear wave velocities derived from sonic log. Pore pressures in the three wells were then predicted using Eaton’s Method. The predicted pore pressures, overburden pressures and poison’s ratio were used to determine fracture pressures using Ben Eaton’s Model. Results showed that there is a suitable drilling margin at all depths only in well G-005. Drilling well A-001 to a depth of 10962.81 ft and K-001 to a depth of 12626.9 ft will fracture the formations because the fluid pressures at those depths approximate the fracture pressures of 8536.7psi and 9506 psi with corresponding gradients of 0.78 psi/ft and 0.75 psi/ft respectively. The implication is that drilling deeper in the field will results in very low seal capacity magnitudes, thereby presenting a higher risk of top-seal failure.
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References
[1] Dickinson G., (1983). Geological aspects of abnormal reservoir pressures in Golf Coast Louisiana†Bull Am assoc. Pet. Geol., v 37. 410 – 432.
[2] Eaton, B.A., (1972). The effects of Overburden Stress on Geopressure Prediction from well logs: Journal of Petroleum Technology, v. 24, 929 – 934. https://doi.org/10.2118/3719-PA.
[3] Fooshee, J. S. (2000). The development of a pore pressure and fracture gradient prediction models for the Ewing Banks 910 area in the Golf of Mexico. Published M.sc thesis, M.sc in Petroleum Engineering, Louisiana University.
[4] Gaarenstroom, L., Tromp, R. A. J., Jong, de. M. C. and Brandenburg. A. M. (1993).
[5] Overpressures in the Central North Sea: implications for trap integrity and drilling safety. In: Parker, J. R. (Editors) Petroleum Geology of the NorthwestEurope: Proceedings of the 4th Conference. Geological Society, London, 1305-1313.https://doi.org/10.1144/0041305.
[6] Jeffrey S. Fooshee, (2009). The development of a pore pressure and fracture gradient prediction models for the Ewing Banks 910 area in the Golf of Mexico. Published M.sc thesis, M.sc in Petroleum Engineering, Louisiana University.
[7] Jiao J.J. and Zheng M. V. (1998), Abnormal fluid pressures caused by deposition and erosion of sedimentary basins. Journal of Hydrology, 13, pp124 – 141.https://doi.org/10.1016/S0022-1694(97)00115-7.
[8] Swarbrick R.E. and Osborne M.J (1996). The nature and diversity of pressure transition zones: Petroleum Geoscience, v.2, p.111-116.https://doi.org/10.1144/petgeo.2.2.111.
[9] Swarbrick R.E. and Osborne M.J. (1998), Mechanisms that generate abnormal pressures. An Overview, in B.E. Law, G.F Ulmishek, and V.I slavin, eds, Abnormal pressures in hydrocarbon environments: AAPG memoir, v 70, 13- 34.
[10] Udo, K.I, Akpan, M.J and Agbasi,O. E.(2015). Estimation of Overpressures in Onshore Niger.
[11] Delta Using Wire-line Data. International Journal of Science and Research, 4(5): 2780-2784.
[12] Yardly, G.S and R.E Swarbrick (2000), Lateral Transfer: a source of additional overpressure: Marine and Petroleum Geology, v.17, p.523 – 538.https://doi.org/10.1016/S0264-8172(00)00007-6.
[13] Zhang, J. (2011). Pore pressure prediction from well logs: Methods, modifications, and new approaches. Earth Science Reviews 108: 50-63.https://doi.org/10.1016/j.earscirev.2011.06.001.
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How to Cite
K. I, U., N. J, G., A. O, A., G. B, A., & M.U, A. (2020). Determining Fracture Pressure Gradients from Well Logs. International Journal of Advanced Geosciences, 8(1), 5-9. https://doi.org/10.14419/ijag.v8i1.29162Received date: 2019-05-04
Accepted date: 2019-08-23
Published date: 2020-02-18