Integrated Research for Carbonate Reservoirs – It Is the Business Question that Mandates the Multi-disciplinary Integration

James R. Markello, ExxonMobil Upstream Research Company, Houston, TX

How many wells are needed to develop a newly discovered, super-giant field? Should a super-giant field on production for 30 years be converted from peripheral water flood to pattern flood? Can declining production in a giant field be economically slowed or reversed? These business-articulated questions have significant financial implications and require integration of geoscience, engineering, and economics to answer. Integrated research for carbonate reservoirs can be defined as the combination of geoscience and engineering concepts, principles, and technologies for solving business-articulated problems related to finding, appraising, and developing hydrocarbons. In the past (1960s to 90s), research programs focused on disciplined-based concepts and techniques, and more recently (1990s and 2000s), integrated research programs have focused on advanced technology and tool development for disciplined-based and some inter-discipline-based problem solving. These are key advances for our science and industry. However, the next level of research requires even more integration of disciplines because it is the research that solves problems articulated in business language.

In 2000, a wildcat exploration well discovered a super-giant carbonate isolated platform (Devonian and Carboniferous age) in the North Caspian Sea. How are the operators going to appraise, develop, and economically produce this field? Of the key development decisions facing the operators, the most important is “how many wells are required to optimally produce the reserves during the length of the production contract?” Is this a geoscience question? Is it a drilling question? Is it a simulation question? Is it an economics question? It is all of the above. No single discipline can fully and confidently answer the question. What is required is an integrated reservoir characterization and geomodel.

A super-giant Middle East oil field (Cretaceous age ramp carbonates) has been producing for over 30 years, has more than 500 wells, is under peripheral water flood, and has recognizable bypass zones. What measures can be taken to ensure maximum economic recovery of reserves? Visualization and volume interpretation tools can image and directly extract facies and rock properties from seismic and log data to populate geologic models with quantitative spatial data. Corendering geologic and engineering data in a visualization environment provides insights into reservoir continuity, segmentation, 3-d distributions of rock and fluid properties, and pressure distribution. Increased seismic resolution and prestack azimuthal seismic data improve ability to map fault and fracture systems. Use of these tools facilitated development of field operation strategies to recover bypassed oil and increase sweep efficiency.

A giant west Texas field has been producing oil from Permian shelfal carbonates since the 1950s and is thought to be at the end of its producing life. How do we address the issues of late life and abandonment of carbonate fields? Management’s decision to retain or abandon a producing field is based on remaining value. Value is an economic calculation based on Remaining Ultimate Recoverable (RUR) reserves. These calculations are based on integrated quantitative reservoir characterization and geologic modeling. Once RUR are determined for a late-in-life field, management can decide, based on business criteria, what actions to take: 1) continue current operations, 2) in-fill drilling, 3) re-completion/work-over program, 4) farm-out the field, or 5) shut-down and abandon the field. In this example, field operations will continue.