Water Induced Compaction in the Ekofisk Field

Water Induced Compaction in the Ekofisk Field J.E. Sylte; J.E. Sylte Phillips Petroleum Company Search for other works by this author on: This Site Google Scholar L.K. Thomas; L.K. Thomas Phillips Petroleum Company Search for other works by this author on: This Site Google Scholar D.W. Rhett; D.W. Rhett Phillips Petroleum Company Search for other works by this author on: This Site Google Scholar D.D. Bruning; D.D. Bruning Phillips Petroleum Company Search for other works by this author on: This Site Google Scholar N.B. Nagel N.B. Nagel Phillips Petroleum Company Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas, October 1999. Paper Number: SPE-56426-MS https://doi.org/10.2118/56426-MS Published: October 03 1999 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Sylte, J.E., Thomas, L.K., Rhett, D.W., Bruning, D.D., and N.B. Nagel. "Water Induced Compaction in the Ekofisk Field." Paper presented at the SPE Annual Technical Conference and Exhibition, Houston, Texas, October 1999. doi: https://doi.org/10.2118/56426-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractOver 7.8 meters of seafloor subsidence has occurred at the Ekofisk Field in the Norwegian sector of the North Sea since the start of production in 1971. Full field water injection was initiated at Ekofisk on a limited scale in 1987. The surface subsidence is a result of reservoir compaction, which is considered primarily to be due to pressure depletion until the early 1990's and water weakening thereafter. Rock compressibility was input as a function of initial porosity and increasing net effective stress (i.e. declining reservoir pressure) in earlier Ekofisk studies. In 1994, under a voidage balancing reservoir management program, water injection was increased sufficiently to stabilize reservoir pressure. However, no reduction in surface subsidence rate was seen. This, in combination with other field and lab observations, led to the conclusion that water was weakening the reservoir chalk and necessitated revising the rock compressibility functions at Ekofisk to include the effect of additional compaction due to the water weakening.The development and implementation of the water induced compaction functions at Ekofisk is presented in this paper. Rock compressibility is now input into the model as a function of initial porosity, net effective stress, and water saturation. As water saturation increases in a model cell due to water injection or water influx, the model cell transitions to a weaker stress-strain curve. The effect of increasing water saturation, and the resulting water weakening of the chalk, is that compaction and subsidence may continue in spite of stable or increasing reservoir pressure. Both laboratory and field data are presented which support the use of the water weakening functions. The development and calibration of these curves is presented, which includes the effects of fracturing, creep, water dispersion effects, hysteresis logic, and strain hardening. A comparison of the calculated and measured compaction and subsidence bowls is also presented. Keywords: enhanced recovery, modeling & simulation, reservoir geomechanics, compaction, production platform, ekofisk field, upstream oil & gas, reservoir characterization, reservoir pressure, reservoir compaction Subjects: Reservoir Characterization, Reservoir Fluid Dynamics, Improved and Enhanced Recovery, Reservoir geomechanics, Integration of geomechanics in models, Waterflooding This content is only available via PDF. 1999. Society of Petroleum Engineers You can access this article if you purchase or spend a download.