Monitoring WAG Pilot at VLE Field, Maracaibo Lake, by Perfluorocarbon and Fluorined Benzoic Acids Tracers

Abstract

It is widely accepted that comprehensive data acquisition programs are necessary for WAG management and pilot project interpretations. Common data acquisition methods used to monitore WAG processes are frequently analysis of separator testing, fluid composition, production/injection rates, pressures injection surveys, gas-oil ratios (GOR) and saturation logging. Chemical tracers have been used as a tool for monitoring water and gas injection, whereas for WAG process no experience in a field has been reported in Latinamerica. At the Lagocinco field, C2/VLE-305 reservoir (located in Maracaibo Lake basin) a WAG pilot project is currently being developed, using a chemical tracers program with Perfluorocarbon and fluorinated Benzoic acids. Five chemical tracers have been injected in both phases (water and gas) during WAG test as a surveillance tool for the process. The aim to inject gas and water tracers was related to use breakthrough time and tracer production/injection history to get a better understanding of dynamic reservoir behavior and to support and upgrade the reservoir model. This paper briefly describes the monitoring process achieved in Lagocinco pilot project, and some results of this monitoring in relation to the WAG process. The result of the first water tracer test has indicated early breakthrough in four wells of the pilot project. One of the wells has increased oil production rate and three of them have maintained oil production rate and have decreased water cut and GOR as consequence of WAG process. The rest of the wells do not show a clear trend in tracer production, confirming heterogeneities in the pilot area. Zones not drained were identified and connection between the injector well and producer were characterized. The results of the first gas tracer have shown different distributions and velocities between gas and water. Finally, the second water tracer breakthrough was observed 3.3 months after its injection, just in one well, declaring that water distribution or path has changed as a consequence of WAG process. Introduction WAG injection processes have become an important IOR technique around the world [1], and have been focus of interest in recent years in Venezuela. This drained strategy is mainly planned to deal with the mayor concerns in Venezuelan oil fields: optimizing natural gas resources and increasing oil recovery factors [2]. Among several candidates, the VLE area was selected to evaluate an immiscible WAG process as representative of large number of deep (>10000 ft) light oil reservoirs in the Maracaibo Lake Basin with similar reservoir characteristics, currently under water injection at an advanced stage of depletion. In Venezuelan western reservoirs there are over 1.1 MMMSTB of oil currently in place in reservoirs with similar conditions. The selection of the VLE area as an Integrated Field Laboratory (IFL) [3] was based on screening criteria for WAG flooding, obtained from successful and unsuccessful worldwide projects [2], analytical simulation, experimental and numerical simulation studies, as well as availability of water and gas facilities. In this paper is described the first immiscible WAG injection pilot at VLE-305 in Maracaibo Lake focused on the monitoring process achieved with chemical tracers and productions curves. A better design, models and operational description of WAG process can be found in previous paper [4].

Waterflooding for lateral anisotropy of porous media

“…Injecting water enables one to sustain the pressure in the formation and thus the initial production rates. When one deals with inside-thepool injection, water is injected through the system of injecting wells following a certain pattern within the oil-pool outline [9]. This is the most intensive system, which enables one to reduce recovery time and increase the production rate.…”

Direct sensitive simultaneous determination of fluorinated benzoic acids in oil reservoir waters by ultra high-performance liquid chromatography–tandem mass spectrometry

“…1). Note that the separated compounds are generally the most frequently used in tracing campaigns [20,21]. Indeed, 2,3-dFBA, 3,5-dFBA, 2,3,6-tFBA, 2,4,6-tFBA, are rarely used owing to their high costs.…”

Cyclic Water Injection Simulations for Evaluations of its Potential in Lagocinco Field

“…The process has been operated successfully with promising results in terms of increased recovery over the ongoing waterflooding project in the field for a period of two years 6,7 . The application of the IWAG method was decided on the basis of screening criteria of successful and unsuccessful international projects, analytical simulations and conceptual numerical simulations 2 .…”