Improved Oil Recovery in Carmópolis Field: R&D and Field Implementations

Abstract

Carmópolis Field in Sergipe/Alagoas Basin in northeastern Brazil is the country's largest onshore oil accumulation at 253 MMm3OOIP and a current total oil production of 2,880 m3/d. Discovered in 1963, it was quickly put into primary production. Water flooding followed in 1971 at the central portion of the field. The combination of adverse fluid mobility ratio, reservoir heterogeneity and the lack of proper selective injection, led to the quick decline of production. Immediately, a major program of selective plugging, stimulation and selective injection was able to stabilize production. Water flooding was then extended to the entire main block of the field. Well pattern was changed from five to nine-spot arrangement, with a corresponding downsizing in well spacing and injection rates. Carmopolis has also experienced several pilot projects for Enhanced Oil Recovery (EOR): polymer flooding, steam flooding and in situ combustion, respectively. This past history of Carmópolis Field and the significance of water flooding to oil production in Brazil with approximately 1,850 MMm3OOIP currently submitted to this method of recovery, led to the selection of Carmópolis as the target for one of the projects in the portfolio of PRAVAP - Petrobras Strategic Improved Oil Recovery (IOR) Program. The scope of this project included the review of the water flooding operation through improved reservoir characterization and flow simulation, as well as the investigation of other IOR methods that might reverse the production declining trend. This paper summarizes the outcome of this project that went from lab research to field testing and led to the approval of operational implementations worth US$ 34 million NPV. Introduction Water flooding has come a long way since its accidental "implementation" in the area around the city of Pithole, Pennsylvania back in 18651. By the mid fifties this improved method of recovery was responsible for more than 10% of the total oil production in the US. By 1986, this share was thought to be in the 50% range2. This scenario is not any different around the world, specially in major producing countries like the former USSR and the Middle East. A good example is the giant field of Ghawar in Saudi Arabia already partially under water flooding. The situation in Brazil is very similar. Close to 2,000 MMm3 of OOIP are currently under the influence of water injection. In the near future water injection rates will reach more than 500,000 m3/d in discovered fields of Campos Basin. In Marlim field alone in the same Basin, water injection is expected to peak around 100,000 m3/d. In fact, the history of water flooding in Brazil dates back to the early fifties and Carmópolis Field onshore Sergipe/Alagoas Basin, as shown in Figure1, is a very representative part of it. Discovered in 1963 and quickly brought on stream, it produces predominantly from the sandstone and conglomerate reservoirs of the Muribeca/Carmópolis formation and secondarily from the deeper Barra de Itiuba formation plus the fractured basement (see Figure 2). Accordingly, oil quality varies considerably throughout the stratigraphic column. General reservoir data is given on Table1 and a good description of the reservoir geology is given by C ndido and Wardlaw3. This paper focuses on the review of the Improved Oil Recovery (IOR) methods tested in Carmópolis field over the last 28 years, the recently concluded R&D project within PRAVAP - Petrobras Strategic IOR Program, and the corresponding field pilot implementations. Past History of IOR Applications in Carmópolis Field. A good review of the past IOR applications in Carmópolis Field is given by Correia4et al., Doria5 and Romeu6et al.

Enhanced Oil Recovery: An Update Review

“… Carmópolis is an onshore heavy oil (22 °API) reservoir with reported in situ-combustion (1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989), polymer flooding (1969-1972 and 1997), steam injection (1978) and microbial EOR or MEOR (2002) pilot projects. The field has been developed mainly by waterflooding [27,[31][32][33][34]).  Karazhanbas is an onshore heavy oil (19 °API) reservoir with documented polymer flooding [35], steam injection [36,37], in-situ combustion and in-situ combustion with foam injection as conformance strategy [37,38]).…”

Microbial EOR: A Quantitative Prediction of Recovery Factor

“…-viscosity reduction by gas (CO 2 , H 2 , N 2 and CH 4 ) production or degradation of long-chain saturated hydrocarbons (Maure et al 2001;Strappa et al 2004;Bao et al 2009); -improvement of rock absolute permeability by the generation of acids that dissolve rock matrix (Yakimov et al 1997); -wettability modification and reduction of oil/water interfacial tension by surfactant production and bacterial presence (Sitnikov et al 1994;Zekri et al 2003;Almehaideb et al 2004;Kowalewski et al 2006;Soudmand-Asli et al 2007; Afrapoli et al 2009); -oil viscosity reduction by biosurfactants (Maure et al 2001;Karim et al 2001;Soudmand-Asli et al 2007); -selective plugging by microorganisms and biopolymers (Yakimov et al 1997;Mezzomo et al 2000;Soudmand-Asli et al 2007); -water viscosity increase due to biopolymers (Sugai et al 1999). The main objective of this paper is the modelling of a MEOR process in which microorganisms produce biopolymers that increase water viscosity and then improve reservoir sweep efficiency.…”

Technologies Trials of Intelligent Field Implementation in Carmopolis Field

“…A recent review of IOR methods through improved reservoir characterization and flow simulation in Carmopolis field resulted in the enhancement of water injection rate and selectivity as one the most determinant issue for the future of oil recovery in the field. 1 Actually, it was proved with the reversion of the declining production trend. Hence, considering waterflooding optimization as the main drive, Petrobras has chosen Carmopolis field as its first Intelligent Field pilot project aiming to get better results on reservoir and production management as in PDO 2 .…”