Murphy Oil entered Malaysia in 1999 with a strategy of combining exploration and development of low risk, shelfal sandstone plays together with frontier, high-impact oil exploration targeting Tertiary deep-water sandstones in the undrilled, deep-water region of Sabah. Interest in the Sabah area had been prompted by the presence of several large, anticlinal thrust structures with evidence of a live hydrocarbon system in the form of gas chimneys in the seismic data and sea floor and ocean surface seeps.
Murphy Oil acquired a substantial acreage position in deep-water Sabah, and the first exploration wells were drilled in 2002. After two unsuccessful wells, the third well of the program discovered the Kikeh Field as a significant oil accumulation in water depths of 1300m, the first deep-water oil discovery in Malaysia (Algar et al., 2007; Masoudi et al., 2013). By 2007, less than 5 years from discovery, Kikeh came on production and 15 further deep water discoveries, including important look-alike oil discoveries such as Gumusut-Kakap, Siakap-North Petai, Jangas, Kikeh Kecil, and Kerisi fields, had been made in the play. Not only was this a remarkable fast track development, but the Kikeh discovery opened up a significant new oil play in an area that until then had been regarded as gas-prone, with little known about the main reservoir objective of Tertiary deep-water sandstones. Detailed regional and field studies have now documented that the reservoirs in the Kikeh Field are deep-water marine turbidite lobes that are interbedded with mass-transport deposits and pass laterally into distal, thin-bedded equivalents of the turbidite sand lobes. Much less sand is recognized as being introduced onto the slope than was originally envisaged, with most sand input being restricted to a short time period in the late Miocene, well constrained by biostratigraphy (Morley, 2014). Turbidites were derived from a narrow shelf and transported down an unstable slope, where syn-depositional-thrusting-modified slope topography and influenced sand distribution down and along the slope. The structural framework differs remarkably between the northern and the southern parts of the Sabah Basin. Hydrocarbons are considered to be sourced from transported coaly organic matter deposited with the turbidites. Selective gas leakage from the crests of the thrust-related anticlines strongly influences the hydrocarbon phase retained in many of the deep-water Sabah fields.
Murphy also opened a new play in the northern area of deep-water Sabah with the discovery of gas in excellent quality, high net-to-gross Upper Miocene sandstones that accumulated in topographic lows (‘mini-basins’) which formed in response to syn-depositional tectonism. Low-relief, combination structural-stratigraphic traps were developed and charged with a mix of thermogenic and biogenic gas. Of particular note is the Rotan Field discovery in Block H in 2007, some 250km NE of the Kikeh Field, which led to the sanction of the Rotan cluster FLNG project in 2014, one of the world’s first of its type, with gas production scheduled to start in 2018.
To date Murphy has drilled 30 exploration wells in deep-water Sabah, resulting in a gross volume of nearly 1.3 Billion BOE reserves being discovered. The discovery of Kikeh opened a new era of technical research into deep-water depositional systems in Malaysia, initially driven by development considerations, but now extended to other exploration opportunities in the area. The geology of these deep-water fields reveals significant information that is being applied to both field development and exploration in the area. Some of the key areas of technical interest Murphy has focused on are:
- The types of depositional systems developed within an active deep-water fold and thrust belt and their evolution into high
net-to-gross sand lobes and laterally equivalent, extensive, thin-bedded deposits containing significant hydrocarbon
- The significance of the control on deposition exerted by mass-transport deposits (MTDs) and their role in defining reservoir distribution and trapping.
- The nature of top seals across structures and the controls on hydrocarbon column heights.
- The nature, distribution, and maturity of source rocks across the Sabah margin.
- The critical aspects of reservoir quality and sand distribution that are essential to understand during the appraisal phase in
order to optimize deep-water development plans.
Understanding these controls on the petroleum system across the Sabah Margin is important, not just in the Kikeh area but throughout NW Borneo, and offers a significant technical advantage in the exploration, development, and evaluation of deep-water areas. Murphy continues to explore in Malaysia and is optimizing the knowledge derived from its deep-water Sabah fields and excellent working relationship with PETRONAS and partners to focus its ongoing exploration activities.