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The oil industry strives to create an international standard for classification and estimation of resources since the 1930s. The goal is to provide investors with information obtained under the same assumptions, as to facilitate the comparison between petroleum companies. In 2007 the four major international organizations, Society of Petroleum Engineers (SPE), American Association of Petroleum Geologists (AAPG), World Petroleum Council (WPC) and Society of Petroleum Evaluation Engineers (SPEE), jointly released a single set of guidelines for classification and evaluation of oil and gas resources, the Petroleum Resources Management System (PRMS, 2007).Several methodologies for estimating reserves can be employed within the PRMS's (2007) premises, which can be classified as deterministic or probabilistic. Unconventional resources emerge as a new frontier for the oil industry, thus implying high uncertainty levels in both technical and economic assessments. The main purpose of this paper is to explore this issue and to propose a correlation-based probabilistic methodology for aggregating oil and gas reserves of conventional and unconventional resources. The methodology is in accordance with the guidelines of the PRMS (2007) and with the new rules of the Securities Exchange Commission 2009 (SEC). The correlation assessment evaluates technical and operational features, and the probabilistic aggregation is performed by Monte Carlo Simulation (MCS).Besides the introductory section, this paper comprises four other sections. A literature review presents definitions of conventional and unconventional resources, and an examination of classification, estimation and aggregation of reserves, important for better understanding the following sections. The third section describes the proposed correlation-based probabilistic methodology. Afterward, a case study presents an application of the methodology. Finally, the last section synthesizes the main conclusions. IntroductionThe estimation of petroleum reserves entails complex assumptions and calculations, once there is uncertainty associated with volumes, recovery, development, and marketability of resources. Unconventional resources bring new challenges to the industry, reinforcing that uncertainty analyses are paramount for estimating reserves.Yet, uncertainty based assessments are not trivial assignments. There must be a thorough understanding of the models to be employed, in order not to overestimate proved reserves.When reserves are determined by probabilistic methods, the arithmetic addition of individual accumulations within an integrated project will understate the aggregated reserves at the proved (P90) level. On the other hand, if full independency is assumed and the accumulations share common risks, the probabilistic addition of reserves will overstate the proved (P90) reserves (Carter and Morales, 1998).This paper introduces a practical correlation-based methodology for aggregating probabilistic reserves from both conventional and unconventional resources. As long as ...

Located in the Middle Magdalena River Valley basin, in the department of Santander, municipality of Barrancabermeja in the rural area of El Centro. La Cira-Infantas is the oldest Field in Colombia and with it, the oil industry was born in Colombia. It has proven reserves of 172 MMBOPD, it reached a production of 65000 barrels in 1939 until it declined to 5000 BOPD in 2005. Through an association contract between two operators, looking for the implementation of new technology, in 2017 45000 BOPD were obtained. During its operation and through the implementation of the secondary recovery method in the field, a high gas and sand content was identified as a problem for high fluid production wells. This has generated premature flailures in the artificial lifting system with Progressing Cavity Pumps during the production of the Arenas C interest zone that raises the costs to the point that makes them economically nonviable. According to the needs of the field and looking for new and better solutions, the design and application of a pump with a special geometry that allowed giving viability to the operation of these problem wells, was performed, thus expanding their run life and reducing costs associated to their intervention. The implementation of this type of pump has allowed a 63% reduction in installation, maintenance and operation costs, and 86% in differed and production loss costs; in general, a 67% economic benefit versus the conventional system was obtained providing technical and economic viability to the development of these reserves.