Quebrache--A Natural CO2 Reservoir: A New Source for EOR Projects in Mexico

Abstract

Abstract CO2 injection is one of the most efficient methods used to improve oil recovery, and, as world statistics shows, its use has increased recently. Under a high crude oil price scenario, field applications of enhanced oil recovery (EOR) processes are becoming economic in today's environment. The natural CO2 sources come to be an excellent opportunity because of its low cost. Since 60 years ago, 2500 km2 of carbonate formations containing CO2 were discovered in North of Mexico. The Quebrache region contains several occurrences of natural CO2 that have been discovered during exploration of oil fields. The CO2 that has been naturally trapped in carbonate formations in this region is present in concentrations that can exceed 90% purity. Due to the high concentrations of CO2, some wells were shut-in 60 years ago, others, have been developed for CO2 production intended for industrial uses and some others as a source of gas lift operations in nearby heavy oil fields. Recently, a plan of acquisition of information and studies to evaluate the CO2 proven reserves has been designed. In addition, analysis of wells deliverability of these natural CO2 reservoirs, located in the southwestern portion of Tampico, has been carried out. In order to understand better this field, a geological model was built and its dynamic behavior and potential was examined through several well tests. Results of the interpretation of these tests showed excellent results associated with a reservoir of good permeability, high conductivity, large drainage radius, etc. According to the geology of this region and the geochemical signatures observed, the CO2 of Quebrache field has an inorganic origin. This paper discusses the evaluation of potential supply of CO2 of Quebrache reservoirs for EOR projects in the North of Mexico. The main region studied contains estimated proven reserves of 1.9 Tscf of CO2; however, this volume could be extended to larger amounts associated to areas under study. The CO2 from Quebrache field could be the beginning of a new era of EOR projects in Mexico. A field example of potential EOR application in a mature oil field is shown. Introduction Quebrache Region contains numerous occurrences of natural CO2 that have been discovered during exploration of oil fields. Most CO2 fields are similar to conventional natural gas fields, with the gas trapped in dome-like structures. The most common reservoir lithologies are sandstones and dolomite, with mudstone and anhydrite being the most common sealing rocks. Carbon dioxide occurs naturally as a result of geologic processes in large, often high-purity (>90 %) deposits in many sedimentary basins. Several CO2 fields in the United States, Hungary, Turkey, and Romania have been or are being developed to provide an efficient source for enhanced oil recovery projects. On average, the global risk of encountering >1% concentrations of CO2 in a gas reservoirs is < 1 in 10, and the risk of encountering >20% concentrations of CO2 is < 1 in 100. However, here is the issue: the mean CO2 content of reservoirs with >20% CO2 is 50% CO2. In other words, when CO2 is abundant, it is frequently so abundant. Furthermore, high CO2 concentrations are encountered in diverse areas. The scientific study of natural CO2 deposits is still at an early phase. Previous work has included documentation of worldwide occurrences of natural CO2 deposits and preliminary assessment of commercial CO2 fields in the USA. This paper discusses the results of the first study oriented to evaluate the CO2 proven reserves of Quebrache field and its potential application as EOR project in a mature field in the North of Mexico.