| Popis: |
Locating and producing bypassed oil due to water injection is one of the most challenging problems in reservoir management. A successful case from Minagish field in west Kuwait is presented. The Minagish Oolite reservoir is a limestone sequence, about 400 ft thick, whose facies consists of high-permeability ooidal grainstones, interbedded with low-permeability facies that act as baffles and barriers. A tarmat zone is known to occur at the base of the oil column leg. Integration of well-surveillance, geological and 3-D seismic data led to a better understanding of the distribution of bypassed oil above the oil-water contact (OWC) and/or tarmat. Also simulation sensitivity study included core studies, analysis of offset wells, and inverted 3-D seismic data indicated the possibility of high oil production rates. A 78° deviated well was drilled down the northeast flank of the Minagish structure. The geological uncertainties associated with this well path were: (1) structural top; (2) reservoir quality; and (3) the presence and thickness of tarmat zone(s). To minimize the risk associated with these uncertainties, two advanced measurement technologies were utilized while drilling. A magnetic resonance imaging LWD (logging-while-drilling) tool was employed to characterize fluids in real time to discriminate bypassed zones of light oil from tarmats. Also, laser-induced breakdown spectroscopy was used to measure the elemental geochemistry of cuttings while-drilling, in order to chemostratigraphically confirm borehole position and identify tarmats. Tarmats could be identified with this technology from elevated levels of Ni and V (and sometime S) in the tar mat zones. Use of these technologies resulted in the identification of two zones of mobile oil in the upper reservoir above the tarmat, as well as a highpermeability layer influenced by water coming from nearby injector wells. |
