Pressure Transient and Production Data Analysis of Horizontal Well in Unconsolidated Formation in Frade, Brazil

Abstract

Frade Asset is a medium-heavy-oil field located in the Northern Campos Basin, approximately 75 miles offshore from Rio de Janeiro, Brazil in 3500 ft water depth. The structure is a low relief anticline with two main fault blocks consisting of four stacked unconsolidated reservoirs. First production started in June 2009, and field development target peak production is 80,000 barrels of crude oil per day. Currently, the field is producing from 9 horizontal oil wells with 3 vertical water injection wells to maintain reservoir pressure. Continuous well monitoring and reservoir characterization is the key to cost-efficient development in this deep-water subsea field. Therefore, most wells in Frade are equipped with permanent down-hole gauges for reservoir surveillance.In this paper, we discuss the impact of three efforts on field performance: 1) monitoring the pressure and production data from horizontal wells since first production, 2) the real-time pressure transient analysis (PTA) of a series of buildup tests, and 3) the transient study combined with long-term production data analysis (PDA). The study results provide insight into formation quality and the change of well conditions with time. The estimations of current drainage area, average reservoir pressure, and original oil in place help to optimize the field development plan. The impacts of pressure-dependent oil properties and rock compaction were also studied, and the first quantitative evaluation of pressure-dependent permeability/porosity reduction was performed using both long-term dynamic well data and laboratory core experiment results. The applications of PTA and PDA in Frade showed that using current advanced technologies properly can yield valuable well and reservoir information from well pressure and rate data.The positive impact of focused efforts to measure and analyze pressure transient and production data, and to use pressuredependent permeability and porosity values in managing a large asset, demonstrated best practices that may be followed in other oil and gas fields.