The G-32 well was the first PWRI (produced water re-injector) to be drilled into the Heimdal Formation at the Grane oil field, located in the Norwegian Sea. Reservoir simulations suggested that G-32 would improve reservoir drainage in the area, providing an important increase in oil recovery through the nearby oil producers. The well was planned as a matrix injector rather than a fractured injector to optimize the reservoir drainage. This gave challenges related to well cleanup and also required good water quality to avoid loss of injectivity by screen/formation plugging. A large effort was made in the preparation phase for G-32 to minimize the risk related to these issues and with the precautions taken, low risk of plugging and loss of injectivity was predicted. This paper will summarize the G-32 experience from both a production and a reservoir management point of view. Simulations and testing performed prior to starting up the G-32, including fracture simulations, produced water analysis, lab tests of the completion fluids and injection experience will be presented. Finally, expectations from the reservoir simulations performed prior to G-32 start-up will be discussed and compared with production experience.
The Grane field is a mature oil field located about 185 km west of Haugesund, in the North Sea, Figure 1. It was discovered in 1991 and the field came on stream September 2003 with license to produce until 2030 (J.A. Haugan et al, OTC 18234). Oil is currently produced from 26 wells, 14 of them are multilaterals. Three injectors are drilled into the reservoir, two gas injectors and one water injector (G-32). Two water disposal wells are injecting water into the shallower Utsira Formation.