Gas-Injection Redistribution Revitalizes a Mature Volatile Oil Field: Cusiana Field Case Study Luis Soto; Luis Soto BP Colombia Search for other works by this author on: This Site Google Scholar Gherson Penuela; Gherson Penuela BP Search for other works by this author on: This Site Google Scholar Ivan Benavides; Ivan Benavides BP Colombia Search for other works by this author on: This Site Google Scholar Monica Martinez; Monica Martinez BP Colombia Search for other works by this author on: This Site Google Scholar Iowany Alfonso Castiblanco; Iowany Alfonso Castiblanco BP Search for other works by this author on: This Site Google Scholar Islena Chaves Islena Chaves BP Colombia Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, September 2006. Paper Number: SPE-103593-MS https://doi.org/10.2118/103593-MS Published: September 24 2006 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Soto, Luis, Penuela, Gherson, Benavides, Ivan, Martinez, Monica, Castiblanco, Iowany Alfonso, and Islena Chaves. "Gas-Injection Redistribution Revitalizes a Mature Volatile Oil Field: Cusiana Field Case Study." Paper presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, September 2006. doi: https://doi.org/10.2118/103593-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 AbstractCusiana is a field of three stacked reservoirs (Mirador, Barco and Guadalupe) of volatile oil with a rich gas cap at the top. After a decade of gas re-injection at the crest of the main reservoir, Mirador, the fluid composition has changed as a result of production/injection. The static framework of this highly heterogeneous reservoir has changed too. For instance, minor faults that were proved to be seals at initial conditions are leaking and fractures that used to be passive have been reactivated today.Initial miscible gas injection strategy in Mirador delivered so far an oil recovery factor (RF) of 50% with remaining oil in areas difficult to access such as an oil rim between the producers and a weak aquifer, poor quality rock layers, and bypassed between the producers and the gas injectors. In Barco and Guadalupe, initial water injection successfully provided pressure support but did not sweep oil as expected (RF= 25%).A strategy was designed to recover additional oil by moving gas injection points to deeper formations, the flank of the structure, injecting at low flow rates from distributed injection points and maintaining a favorable voidage replacement. This strategy was based on a synergy among the three reservoirs, which allowed well conversions, rehabilitation of 9 shut-in wells to be injectors or producers and conversion of 10.5 km of water injection flowline, which expanded the gas injection network.After 40% of the strategy implementation by the end of 2005, 1.8 MMSTB of incremental oil has been recovered, reducing the monthly field oil rate decline by half. This success has "boosted" the continuation of the gas injection redistribution strategy for 2006.This paper describes the geological and reservoir engineering modeling that was performed to design the gas injection redistribution strategy in this mature field.IntroductionAt discovery, Cusiana field was over 1 billion barrels accumulation divided into three stacked reservoirs (Mirador, Barco and Guadalupe) and two fluid systems both volatile oils with a rich gas cap at the reservoir top1. After a decade of 1.3 bcf/d gas cycling in the main reservoir, Mirador, reservoir fluid composition has changed in both the vertical and the areal extent as a result of production and injection activities in a highly heterogeneous reservoir.Not only the fluids but also the static framework has changed too. For instance, intra-faults that were proved to be seals at initial conditions are leaking today, fractures that used to be passive have been reactivated today. And even the business driver has changed from a 100% oil market is moving gradually into gas sales. As a consequence, the reservoir management strategy must evolve along with the new situation.Field BackgroundGas cycling, water injection and blowdown mechanisms were implemented in different areas or formations to develop the Cusiana field. From these strategies, the gas cycling has provided the highest recovery factor due to the miscible displacement process2.Nevertheless, early gas breakthrough due to fingering impaired oil production leaving un-swept areas and promoting ineffective dry gas cycling. In addition the water breakthrough affected lifting capacity and even caused lost of producers. This channeling effect is believed to be a consequence of the reservoir heterogeneity as reflected by current GOR distribution (Fig. 1).The heterogeneity has been studied considering the simultaneous interaction of many stratigraphic and structural elements at different scales3. These characteristics make Cusiana field a set of highly heterogeneous reservoirs (Fig. 2).The initial strategy of crestal gas injection and down flank producers led to a good oil recovery of 50% in Mirador by 2005. Despite of that, the recovery mechanism has become less effective over time. Lack of flexibility in gas injection scheme (wells and flowlines) has increased the effect of heterogeneity and promoted the establishment of defined gas injection corridors.Remaining oil is now difficult to access from existing well configuration and incremental reserves are not enough to afford sidetrack or new well drilling campaigns due to high associated costs in a challenging drilling environment4,5. Keywords: artificial lift system, gas lift, waterflooding, heterogeneity, gas-injection redistribution revitalize, oil rate decline, Mirador, Cusiana field, Barco, reservoir Subjects: Artificial Lift Systems, Improved and Enhanced Recovery, Gas lift, Waterflooding, Gas-injection methods This content is only available via PDF. 2006. Society of Petroleum Engineers You can access this article if you purchase or spend a download.