Janjuhah, Hammad Tariq (Universiti Teknologi PETRONAS) | Ahmed Salim, Ahmed Mohammad (Universiti Teknologi PETRONAS) | Ali, Mohammad Yamin (PETRONAS Research Sdn. Bhd) | Ghosh, Deva Prasad (Universiti Teknologi PETRONAS) | Amir Hassan, Meor Hakif (University of Malaya)
Carbonate platforms in the Central Luconia is the most important province in the Sarawak Basin for gas production in the region. These carbonates are economically significant containing 65 trillion cubic feet of gas in place with minor contribution of oil rims. Over 200 carbonate buildups have been seismically mapped, out of which 120 still remain undrilled. These provide potentially attractive exploration targets and incentives to discover the remaining hydrocarbons in the region. The Central Luconia Province is a key geological unit for understanding the distribution of hydrocarbon resources in Malaysia. Although the first hydrocarbon was discovered more than 60 years ago,nevertheless, little effort has been made until now to address the proper facies scheme, cyclicity and reservoir quality of these Tertiary carbonates of Central Luconia.
This paper documents the various facies based on the qualitative and quantitative description of cores of five wells cores in three different carbonate platforms with different cyclicity, carbonate buildups and reservoir quality. Detailed petrographic and petrophysical data have been validated to establish the standardized facies scheme. The combination of facies with cyclicity is very important to understand the depositional setting of the sediments and reservoir behavior. Because the sediments which are deposited during the transgressive phase can act as a barrier for hydrocarbon to migrate vertically.
Eight facies types have been recognized qualitatively and quantitatively (
Six regressive cycles are recognized within the carbonates based on the core and well logs. The 0.1 to 50m thick facies is stacked in vertical sequence within the 50-100m thick transgressive and regressive cycles. The reservoir intervals are divided into seven zones, based on porosity, permeability and major diagenetic events, representing high and tight porosity. The best reservoir intervals are consistently found in most of the regressive cycles, which composed of skeletal lime packstone, coarse coral fragments with touching vugs. The systematic semi-quantitative characterization, portrayed the buildup as coarse limestone with cyclical grain size variations creating high-permeability layers.
Alwi, Noraliza (PETRONAS Research Sdn Bhd) | Borhan, Noorazlenawati (PETRONAS Research Sdn. Bhd) | B M Ibrahim, Jamal Mohamad (PETRONAS Research Sdn Bhd) | Paramanathan, Subashini (Shell EORC) | Bouwmeester, Ron (Shell EORC)
Alkaline Surfactant Polymer (ASP) flooding has been identified as one of the best EOR methods to further recover the trapped oil in Malaysian maturing fields. ASP flooding application promises a huge incremental recovery factor based on recent successful implementation on offshore fields in other part of the world. The application of ASP flooding has been identified for pilot in North Sabah reservoir which is currently flooded with seawater since March 2011. Despite the promising recovery factor from the pilot laboratory and simulation study with incremental recovery of >80% above waterflood, the ASP flooding success always comes with risks and challenges.
Two major challenges behind the success of ASP flooding are the formation of scales near wellbore due to the high pH of the alkaline in the injection fluid and the tight micro-emulsion which produced back in separator vessel which contains surfactant breakthrough. The identified pilot North Sabah reservoir which is currently been flooded with seawater is expected to further worsen the scaling effect due to the high divalent cation concentration (i.e. Ca2+ and Mg2+) in seawater. In addition, the high seawater cut causes a very tight micro-emulsion which is very difficult to manage. These challenges cause formation damage which impact injectivity and flow assurance issue to the production facilities as well as impair the crude quality and sellability.
This paper will discuss in great detail on the lab test results which was designed based on the reservoir simulation ASP flooding study in North Sabah reservoir. Based on the in-situ produced water and chemical breakthrough simulated, this paper describes the extent of emulsion and scale severity at various ASP to water ratio, extensive performance tests evaluating the demulsifier and the scale inhibitor and discusses on the challenges in finding the suitable demulsifier and scale inhibitor at the simulated breakthrough condition.