|Publisher||Society of Petroleum Engineers||Language||English|
|Content Type||Conference Paper|
|Title||Horizontal Wells Pressure Build Up Analysis in Orinoco Heavy Oil Belt|
|Authors||M. Briceno, PETROZUATA C.A.; L.E. Summers, CONOCO, Inc.; O.J. Quijada, PDVSA EPM|
SPE International Thermal Operations and Heavy Oil Symposium and International Horizontal Well Technology Conference, 4-7 November 2002, Calgary, Alberta, Canada
|Copyright||Copyright 2002,SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium and International Horizontal Well Technology Conference|
The innovative application of horizontal drilling technology has made the Petrozuata development project in Venezuela a great success. Petrozuata is the first of four strategic associations implementing an integrated development in the Faja trend, which contains 1.36 trillion barrels of oil in place and is one of the world's largest heavy oil accumulations. The joint venture of Petroleos de Venezuela, S.A. (PDVSA) and Conoco, Inc., drilled 101 single lateral and 140 multi-lateral horizontal wells in the Zuata Field from 1998 to 2001 as a means of delivering production rates of up to 3000 BOPD per well from reservoir sands of 8(° to 10° API oil.
Well test interpretation and analysis techniques have been applied to both single and multi-lateral horizontal wells. This paper summarizes the methodology developed to analyze pressure build up (PBU) tests in the single lateral horizontal wells and recent experiences with the application of state of art PBU analysis techniques in the Zuata field wells.
Because of the geological complexity of the fluvial-deltaic reservoir sands and the peculiar transient pressure behavior, it was necessary to integrate analytical techniques that identified the various flow regimes with numerical analysis that further quantified the analytic interpretation. The integrated approach allowed for improvements in the conventional analytical interpretation and provided a basis of incorporating refinements in the reservoir description when combined with geological and petrophysical data and interpretation.
Petrozuata is a joint venture company between Conoco Orinoco Inc. and PDVSA that is developing extra heavy crude oil (8° to 10° API) in a 74,000-acre block containing more than 21 billion barrels of oil in place within the Zuata field, Faja del Orinoco in Venezuela (Figure 1). From 1998 to 2002, Petrozuata drilled 241 wells consisting of multilaterals and “fishbones”. The development wells are the initial phase of a 35-year project that will require a total of 748 wells producing at a sustained rate of 120 MBOPD.
Analysis of data from a combination of 3-D seismic, extensive vertical stratigraphic well penetrations, and initial single lateral horizontal well performance confirmed that the Oficina reservoir is more complex than originally expected. In general the reservoir is comprised of a series of relatively thin, disconnected sand bodies (Figure 2). The added geological complexity has resulted in significantly less connected oil in place per well and has also impacted well performance. To offset the effects of the heterogeneities, Petrozuata applied new technologies in designing, drilling and completing multilateral wells to increase well rates, improve recovery and to optimize the number of wells needed for the development1. To help understand the depletion efficiency in these complex sands, each well was equipped with downhole pressure gauges with surface read-out.
Analysis of PBU's in these wells has helped define the geological description, factors affecting well productivity and different flow patterns in comparison with flow regimes expected.
Modern transient analysis techniques are based on pattern recognition of the pressure derivative to assist in selection of the appropriate reservoir model. Well test interpretation involves the analysis of pressure responses to derive reservoir and near-well properties for a selected analytical model, based on geology, petrophysics and well geometry. However, the analytical model should also be supported by a numerical model, which permits more variability in the reservoir geometry, and hence a better interpretation.
For the Petrozuata project, the PBU data can be combined statistically with other data to analyze and identify different flow regimes and pressure transient behavior. Petrozuata's experiences in the interpretation of single lateral horizontal well tests in fluvial-deltaic heavy oil reservoirs are presented in this paper.
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