Integration of Old and New Measurements to Optimize Redevelopment of the Lower Lagunillas Reservoir of Bloque IV, Lake Maracaibo, Venezuela


The Lower Lagunillas of Bloque IV of the Bachaquero field is a supergiant reservoir that has been in production since 1956. We have carried out a pilot reservoir characterization study in the central part of the field, in which we have integrated all the available data into three-dimensional (3D) reservoir simulation models whose purpose is to optimize redevelopment of the area with horizontal wells. An analysis of the history of production was undertaken to gain an insight into the reservoir dynamics. This analysis indicated the inefficiency of gas injection in providing pressure support to the pilot study area and demonstrated the presence of active aquifer encroachment from the south. Anomalies in production behavior and fluid characteristics indicate both lateral and vertical compartmentalization of the reservoir. We have integrated Fourier transform infrared (FTIR) measurements of mineralogy from old cores with a comprehensive logging suite in a new well to re-evaluate older, sparse logging suites. The application of a mineral-based log evaluation and high-resolution processing of the new logs has led to a significant increase in estimates of oil initially in place in the study area. We have used a novel approach to estimate permeability in all wells in the study area. Combining these new evaluations with a revised geological model enabled us to recognize 11 geological layers throughout the area. Formation pressure measurements confirm that partial barriers to vertical communication exist between most of these layers. Cased hole saturation measurements and historical production data indicate an uneven sweep of these layers, such that five layers contain bypassed oil that could be recovered by horizontal wells. We have constructed very detailed simulation models that describe the lateral and vertical variation in petrophysical properties of each of these layers. These models have been used to select the optimum locations for horizontal wells and to optimize their drilling sequence and design. It is estimated that each of these wells could recover 1 to 1.5 million stock-tank barrels (STB) within 5 years. The first well drilled as a result of this study has produced dry oil at rates up to 469 BOPD from a zone not previously considered as a pay zone.


Mining Engineering

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Article - Journal

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© 1998 Society of Petroleum Engineers (SPE), All rights reserved.

Publication Date

01 Jan 1998