RIASSUNTO
Abstract
Bream Field, in Australia’s Gippsland Basin, was originally developed in 1987 as a thin oil column development with gas cap re-injection. A satellite platform was installed in 1996 to capture resource not reachable from the original platform. After achieving 68% recovery, oil rates had fallen to the point that gas cap blowdown was commenced. Given the extremely strong natural pressure support seen in the Gippsland basin, a controlled blowdown was carried out to maximize oil recovery during gas export. As the water level approached the top of the structure, an assessment was carried out to determine the best use of the field infrastructure.
The result of this effort was a decision to utilize the field for gas storage while simultaneously achieving enhanced recovery. By refilling the Bream reservoir with dry gas from the Longford gas plant during the summer months, high liquid yield fields are able to be produced consistently throughout the year. Additionally, Bream gas deliverability capacity is increased in the high gas demand periods. As the dry gas moves through the reservoir, it contacts both residual oil and rich gas, becoming re-saturated with gas liquids. When this gas is re-produced, it will yield more liquids, raising the overall recovery of the oil by approximately 1%. Re-injection into the Bream reservoir began in 2013 and is proceeding as planned.
This paper will discuss the history of the Bream development, highlighting the analysis and planning that led to the recently implemented project. The management of this field demonstrates a number of techniques for maximizing hydrocarbon recovery over the life of a field, as well as considerations for maximizing economic value of the infrastructure.
Background
Bream Field, in the southwestern part of the Gippsland Basin (Australia), was originally discovered in 1969 and first developed in 1987. It is produced by the Gippsland Basin Joint Venture (between Esso Australia Resources Pty Ltd and BHPBilliton Petroleum (Bass Strait) Pty Ltd), with EARPL as the operator. GBJV offshore infrastructure includes 19 platforms, 4 subsea installations, and a network of pipelines feeding the Longford Gas Plant (see Figure 1). Approximately 98% of the production from the basin has come from the GBJV, since start-up in 1969. Bream Field and its development have been described in several publications, including:
Shaw (Shaw, 1991) described the mechanical aspects of the initial horizontal drilling program;
Titus (Titus, 1997) described the design and installation of a second satellite platform;
McKerron et. al. (McKerron, 1998) described the development process and results from that second platform;
Fish and Zajdlewicz (Fish, 2004) described the strategy for maximizing recovery during blowdown.
The Bream development history, along with the forward plan described here, provide an interesting case study that demonstrates how available technology and the market demands drive development decisions.