The Exploitation of Heavy Oil From Middle-Deep Reservoirs: Horizontal Well Completions at the Oritupano-Leona Field In the Eastern Venezuela Basin

摘要

Since Petrobras Energia Venezuela took over the Oritupano-Leona Unit by agreement with PDVSA in March 1994, turned out a great challenge for the company about how to increase and improve not only the field potential but the reserves enhancement too. Low to high liquid rates horizontal wells were implemented in order to defeat one of the most challenging issues at the company: The exploitation of heavy oil from middle-deep reservoirs.rnNumerical simulations along with geological studies were conducted to define the best strategy for performing new horizontal wells. Drilling and completions started five years ago making the first steps to get a technical and economical performance for well productions and at last, three stages were done. Stage Ⅰ considered low liquid rates horizontal well completions ranging from 1,500 BFPD through 4,000 BFPD. Stage Ⅱ was a little bit aggressive increasing rates from 7,000 BFPD through 10,000 BFPD and finally we went Stage Ⅲ, where our goal was to reach more than 20,000 BFPD. All cases observed that transient flow regime where water conning threats have to be faced before reaching semi steady state flow, lasts between 8 to 10 months. During these periods, different productions strategies were implemented. Looking at adverse factors such as oil gravity ranging from 8 API to 12 API, reservoir depths from 7,500 feet to 9,000 feet, scales precipitation possibilities and a very strong aquifer presence with similar physical-chemical properties throughout the geological column, let anybody to think that it was obvious that obtaining these 20,000 BFPD, not reaching water conning effects, represented a very risky feat for the company. The R sands in the Oritupano C field, one of the most productive blocks at the main Oritupano-Leona System, became as a remarkable experience after the nation wide largest horizontal well completion (Hz-13) with more than 20,000 BFPD; 12 API; 800,000bls cumulated oil and no waterrnconning effects in the last 10 months. Some other areas are giving same results such as TU sand in the Oritupano B field. Results show that improve oil recovery (IOR) from middle-deep horizontal wells in Eastern Venezuela have boosted the heavy oil production with no steamflooding and diluent injection techniques. Yet there are some issues to face such as emulsion formation in the early production during transient flow and the reservoir fingering or channeling effects that might prevent a second line of well construction. More statistical information together with more simulation studies will contribute to reduce the uncertainty in forecast for heavy oil produced horizontal well projects: The challenge is still ongoing.