Thinly bedded reservoir study in the deep-water area, offshore Sabah, Malaysia, was performed with the primary objective of improving the understanding of its complex geology. The nature of reservoirs, which are predominantly thin-bed and laminated sandstones of submarine fan environment, contain a high level of uncertainty in its lateral continuity. Standard shaly-sand log analysis methods contribute pessimistic values of porosity and water saturation when applied to these reservoirs. Few techniques are then presented for the determination of these rock properties, which are more reliable with core and production data. Core grain-size analysis of these reservoirs shows that clay content is generally low but the silt content can be significant. Furthermore, log responses show that porosity distribution and mineral-conductivity are influenced mainly by the silt-size particles. A sand-silt-clay (SSC) model was then developed from density-neutron crossplot, which model is also used to determine porosity and water-saturation in addition to volumes of lithology components of the reservoirs. Furthermore, other petrophysical technique, called SHARP, uses 1D convolution filters to match thin bed modelled log curves to their corresponding measured responses. A petrophysical evaluation using standard resolution logs and the thin bed resistivity (SRES) from image response are used to develop a thin bed model that yields high resolution logs. For zones where the resistivity image indicates significant thin bed development, the standard petrophysical analysis should also indicate the existence of free fluid. Although the porosity tools cannot resolve the thin beds, they nevertheless represent the bulk volumetric over the interval, known as Thomas-Stieber-Juhasz (TSJ) method, and would be able to differentiate between porous zones with lower clay volume versus porous shales with high clay volumes. The main point is that if a thin bed interval has some calculated free fluid volume using standard resolution logs, then a thin bed analysis is warranted.

The Berantai Field is a marginal sand-prone formation located offshore in the Malaysian Peninsula, and its development was chosen for Malaysia's first and second Risk Service Contracts (RSCs) to provide gas production within two years of the Field Development Project (FDP)'s execution. This field was initially considered as marginal with only an estimated 44 mmstb of oil and 440 mmscf of gas. A key performance requirement was to complete and produce the gas wells, sand free at the targeted production rate of 150 mmscfd. However, during development of the field, up to twenty multilayered, unconsolidated sand formations that had not been forecasted in the FDP were discovered, increasing the challenges for the completion strategy. The dual-string single-trip multi zone (STMZ) system was selected for the completions, as this technology had been proven to provide cost-effective, single-trip gravel-pack applications that could reduce overall cost, since the gravel packing for multiple zones could be performed in a single trip. Although completing long intervals has unique challenges for fixed- interval spacing, and the initial campaign presented other challenges, all seven wells were successfully delivered. A total of thirty one zones were treated. One of the wells not only had six gravel-packed zones completed in one trip, but also had the world's longest concentric wash pipe used in any dual string STMZ completion. This paper will show how proper completion planning and dual string STMZ technology enabled the operator to deliver the committed gas production, saved ~150K USD per gravel-packed zone, and reduced approximately 2.2 days in average rig time per well. The challenges addressed during this campaign, the methodology followed in the completion design, detailed completion and pumping strategy success factors, and the production results obtained from this marginal field development will be presented.