MPD Applicaton on ERD Well Offshore Venezuela – Managing Bottom Hole Pressure within Narrow Window in a Faulted Limestone Formation with an Static Underbalanced Drilling Fluid

Abstract

This paper describes the use of the Managed Pressure Drilling technology in the largest offshore gas field in Latin American and the first offshore gas field to be brought to production in Venezuela. Managed Pressure Drilling technology with the assistance of Continues Circulation System was successfully implemented in the drilling of an extended horizontal section across a fractured and faulted limestone reservoir in an offshore gas well in the Venezuela Perla field. This paper presents the planning, operation and challenges faced while drilling across the reservoir and while running the production liner, how the severe losses were managed keeping the bottom hole pressure within a narrow mud window and preventing gas influxes with the assistance of the Automated MPD system Managed Pressure Drilling (MPD) is a technology where well control is maintained during the drilling operation by using a constant bottomhole pressure through the application of a surface back pressure (SBP) with the utilization of MPD chokes and a Rotating Control Device (RCD). The accurate measurements of flow in/out are essential to the MPD system to provide early indication of well losses or gains with the use of mass flow meter to measure flow rate and mud density (Coriolis meter). The closed fluid system provides high resolution of mud density, flow rates and pressure with the ability to direct measure formation pressure at key places and fracture gradients without detaining the drilling operation. The Perla field is located in the CARDON-IV block in waters of the Golf de Venezuela, 50 km offshore Peninsula Paraguana. Perla consists of one production platform with a total gas production 500 MMscfd dedicated for local consumption. The objective reservoir is the lower carbonate at a depth of approximately 9000ft SS. The thickness of the reservoir is approximately 700ft. The anticipated production from each well is in the order of 80 MMCFD to 135 MMCFD with an initial condensate yield of 25-30 BC/MMCF. In previous wells, severe lost circulations were encountered while drilling the Lower Carbonate Reservoir which has a formation pressure of 9.8 ppg at the top. Several LCM pills and eventually cement squeezes were required to control these losses. In some cases, major losses were encountered, resulting in early termination of the section. Losses of this magnitude are due to a fractured carbonate and the crossing of several faults along the open hole.