TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe 21 Sand reservoir in the Mahogany field has a 63-75 ft oil leg overlain by a gas cap and underlain by water. In order to utilize reservoir energy and efficiently develop the field, the oil reserves must be recovered prior to producing the gas which is dedicated to the Atlantic Liquified Natural Gas plant in Trinidad. A horizontal well program was planned to develop the oil leg. An in-house reservoir simulator was used to predict performance of the oil wells.The 21 Sand is 400' thick and has been segregated into 7 stratigraphic intervals. One hundred and twenty feet (120 ft) of core was acquired through these intervals and the petrophysical properties were measured on representative plug samples. This data was then correlated to well log data. Porosity-permeability flow units were then derived for optimum well placement. Modified-Lorenz plots (Ref. 1) were used to identify the units that would contribute to the flow and those that would act as baffles. Three dimensional visualisation models were then used to place the horizontal wells in high quality reservoir rock. Additionally, placement of the development wells for the deep gas reservoirs was designed to provide vital structural and stratigraphic information for potential heel and toe points for horizontal drilling.This paper describes how all this work was compiled into a simulation model which has successfully predicted the current well producing rates and pressure draw down.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHorizontal oil well drilling, completion and production techniques have continued to advance through the use of shared learnings and new technology as applied in the most recent BP Amoco field development in Trinidad. The Mahogany field is being developed to supply gas to the Atlantic LNG plant in Trinidad. The 21 Sand reservoir in this field has a 60 foot oil column overlain by a 400 bcf gas cap and underlain by water. As with other fields in Trinidad that have thin oil columns horizontal well technology was selected as the preferred method to develop the Mahogany 21 Sand oil leg. During the front end loading design phase of the Mahogany field development an extensive review of evolving technology and recent world wide experience was undertaken. As well, the front end loading involved a review of the BP Amoco Immortelle (Trinidad) horizontal well program which was in its third phase as the Mahogany front end loading was being completed.The critical success factors that emerged from the front end loading review were well placement within the oil column, avoid drilling poor quality reservoir, avoid undulating wellbores, the need to understand well performance with very low drawdowns, the need to land the well in the right place and at the right angle. All of these issues were addressed in the Mahogany horizontal well designs and have been successfully implemented.The front end loading work and continuing optimization of the well designs has resulted in a highly successful 21 sand oil development which is expected to deliver economic results superior to the authorized metrics.

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