3D-All-The-Way™ and F6 Further Development

Abstract

It is well established that working in an integrated team is a more valuable and efficient way of working. But how to ensure that the maximum value is harnessed from those multi-disciplinary teams? The approach chosen in Shell Malaysia is to turn the typical sequential study flow pattern from seismic-static-dynamic-development plan into a truly parallel one. This means: integration through iterations, where the end objective is worked from a 50/50 solution iteratively towards the 80/20 or more. This is what 3D-All-The-Way™ is all about! This paper describes a live example of this way of working applied to the further development of F6, one of the largest gas fields operated by Shell Malaysia in Sarawak waters.

The F6 field is located in the Central Laconia carbonate province, some 180 km offshore form Bintulu. The field has been on production since 1987, and over half of the reserves produced have been drained by 11 slightly deviated wells from its own standalone platform facilities. F6 existing well capacity is coming under threat with regional aquifer rise and localised coning around wells. As a result, further development is required to maintain the capacity at the level required from the supply plan, and to ensure that reserves are protected against the un-even rise of the aquifer in the field. This redevelopment study used the most recent data available, ranging from 3D seismic, to pressure and contact surveillance.

The business value of the 3D-All-The-Way™ approach is (1) speed: as the redevelopment plan and supporting studies are executed in a reduced time-frame (2) efficiency: as from an early stage and continuously through the study work un-realistic subsurface realisations and development options are screened out, (3) quality: the overall robustness of the subsurface work is improved, as every discipline are contributing simultaneously, and at each iteration. Finally, as an added bonus, the teamwork is more enjoyable and cross-discipline learning is enhanced.

The methodology followed by the F6 further development team is being applied to other Field Development Plans within Shell Malaysia E&P, with the same success, saving time, improving the quality of the models and of the decisions.

Introduction

F6 is the largest gas field within the Shell Sarawak portfolio, with a GIIP of ca 7 Tscf. The field covers a large area of approx. 168 km2 and has a gas-bearing interval of over 850 feet thick at its highest point. It is an elongated carbonate build-up, with steep flanks and a generally flat top of Miocene age. Gas is contained in three major zones: the highly prolific Zone1, which forms the upper part of the build-up and contains less than 10% of the GIIP, the lower grade Zone2, which extends over the central half of the build-up and the intermediate quality Zone3 which contains about 2/3 of the gas in place (figure 1).

The field is maturing, with over half the reserves produced. Commissioned in 1987, the field has been producing at rates close to platform capacity (700 MMscf/d), from 11 deviated wells. Half the wells were completed on Zone3 and the other half on Zone1.

Field performance had been indicating a weak aquifer drive. Water contact movement monitoring has been a key surveillance activity from production start-up, since gas-water coning and aquifer rise represent a key risk to well capacity and to some extent reserves. The first water-breakthrough occurred in late 2001, and since then the primary mitigation had been to perform water shutoffs by cementing off water producing intervals and when possible recomplete higher up on Zone1 and Zone2 (figure 2).

However, by then a longer term strategy was required to safeguard reserves and capacity in the field against the water rise. A 3D survey was acquired in mid 2002 to support an infill drilling campaign and a potential field re-development.

The reservoir management strategy for the field was clear: in the short-term: maintain capacity with non-rig interventions, the mid-term: increase capacity with infill wells, and the long-term: safeguard and increase reserves with a re-development (figure 3)