Comprehensive Fluid Compositional Analysis Program to Support the Interpretation of Chichimene Field In-Situ Combustion Pilot

Abstract

Summary The evaluation of enhanced oil recovery (EOR) methods in Colombia has been very active during the past decade. One of the most recent and promising pilots is the in-situ combustion (ISC) in Chichimene field, starting in September 2019. Based on international ISC field experiences, this pilot represents a unique case study given the depth (≈8,000 ft) of this heavy crude oil (9 °API) reservoir. The pilot project consists of one injector, seven producers, and two temperature observation wells between the injector and first-line wells. Production response shows encouraging results. Its interpretation is supported by a comprehensive fluid compositional analysis, which is the main objective of this paper. This paper describes the compositional analysis of produced fluids (gas, oil, and water) and the influence of the current flow assurance program. Geochemical simulations support the evaluation of scaling tendencies, and possible corrosion trends are based on iron and manganese concentrations following the National Association of Corrosion Engineers (NACE) standards. Crude oil analysis is based on conventional techniques (i.e., acid number, distillation curves, etc.) and biomarkers to infer possible thermal maturation changes in the produced oil. Results confirm predicted cycles of CO2 and H2S during the planning of the monitoring program. The solubility of both gases in water leads to their acidification and the formation of carbonate and sulfate scales characterized in production wells. The precipitation of solids was also influenced by the N2-based H2S scavenger decomposition downhole due to the water pH increment observed with the dosage increases. The scaling tendencies did not impact the productivity due to the high reservoir permeability. The precipitation of iron species made it difficult to interpret NACE standards to infer corrosion except for wells shut in for more than 2 months showing a higher concentration of Fe and Mn. However, a recent casing inspection job at one of the first-line producers shows no corrosion signs. Heavy metals such as nickel and vanadium were analyzed in water to infer the possible corrosion or thermal cracking of porphyrins in crude oil. Changes in the paraffinic fractions and biomarkers (i.e., methyl phenanthrene index, mono- and tri-aromatic steroids) suggest an increased thermal maturity of the produced oil. The robust monitoring program has provided important insights from the ISC process and flow assurance strategy supporting possible expansion plans. This study provides valuable guidelines for monitoring programs based on compositional analysis of produced fluids, including the influence of production chemistry. Lessons learned through the Chichimene ISC monitoring program can be valuable in interpreting thermal and potentially nonthermal EOR projects.

Workflow of the In Situ Combustion EOR Method in Venezuela: Challenges and Opportunities

“…Figure shows an example of a microscopic image of a stable water-in-oil emulsion of a dead oil sample (cold production) with 6% wt of water from the FPO . Operational problems associated with the formation of emulsions have also been reported for projects in Colombia (Figure ) and in the USA …”

“…Figure 19 shows an example of a microscopic image of a stable water-in-oil emulsion of a dead oil sample (cold production) with 6% wt of water from the FPO. 118 Operational problems associated with the formation of emulsions have also been reported for projects in Colombia (Figure 20) 117 and in the USA. 60 A Colombian study of water-in-oil (W/O) emulsions during an ISC project for three different crudes has been reported by A ́lvarez-Marti ́nez (2021).…”

“…Fluid production should be constantly monitored to detect compositional changes related to the ISC process at field conditions. , The separation of produced fluids (water, oil, gas, and sand) in highly viscous oil reservoirs in the FPO is a frequent operational challenge, both in cold production and after the application of EOR processes, such as ISC tEOR.…”

“…Methods to control O 2 breakthrough consist of monitoring the temperature, composition of the produced fluids and fluid saturations at reservoir conditions, and analysis of injectivity and connectivity to identify heterogeneities and flow patterns. This allows for the optimization of the design and configuration of the pilot wells (nitrogen connectivity tests). , It is reported that optimization of the distance between the injection and horizontal production wells together with optimization of the air injection rates are the key parameters in reducing the risks of O 2 breakthrough. , The air injection rate is an important parameter to provide the heat necessary for thermal cracking reactions (i.e., deposited coke). Exceeding air injection could affect the general performance of the ISC technology, as high gas production is difficult to handle at surface conditions (high temperatures in wells, impact on artificial lift systems, etc.…”

“… Evaluation of the pH effects on oil emulsions at different water–oil ratios from microfluidic experiments: Chichimene Field-Colombia In Situ Combustion Pilot. 117 Reprinted with permission from Manrique et al, 2022, 117 SPE-209390-MS, Copyright Society of Petroleum Engineers, 2022. …”