St Joseph Chemical EOR Pilot – A Key De-risking Step Prior to Offshore ASP Full field Implementation

Abstract

Chemical enhanced oil recovery (cEOR) is a complex process which exhibits a number of risks and uncertainties. A successful chemical EOR implementation depends on the success and the ability in addressing all these risks upfront and one of the important de-risking steps is the piloting process before full scale implementation. St Joseph is an offshore field in North Sabah region of Malaysia chosen for chemical EOR implementation. In line with the implementation of chemical EOR, there are a number of uncertainties and risks associated with such a development. Some key uncertainties are generic to cEOR development, such as the heterogeneity, chemical effectiveness, emulsion, production of sales specification oil, etc. However, there are certain risks and uncertainties that are typical for this particular field, such as fractured injection, offshore environment, large secondary gas cap, etc. In order to de-risk the full field development and get a better handle on the risks and uncertainty, a pilot is planned. The paper discuses the approach taken for the pilot selection, which includes the qualitative and quantitative assessment of pilot types vis-à-vis key risks, the workflow towards designing the pilot, the modeling approach followed, the facility concept of the design, and injectivity modeling, leading to final pilot design. The paper also touches upon the data acquisition and surveillance plan to analyze the pilot performance and quantitatively address the key risks. In addition, the risks and uncertainties of the pilot implementation are also discussed, together with the mitigation and remediation methods. The pilot study resulted in the detailed pilot design and data gathering plan. The results of the pilot will be used to determine if chemical EOR is viable for full field development at St Joseph.

Status of surfactant EOR technology

“…Before carrying out a field pilot, generally a single well (chemical) tracer test (SWTT or SWCT) is conducted. The SWTT is sometimes called chemical huff and puff (Chai et al, 2011). During a SWTT, a slug of surfactant solution is injected in a well and the oil saturation before and after the surfactant injection is measured.…”

An integrated Shannon Entropy and reference ideal method for the selection of enhanced oil recovery pilot areas based on an unsupervised machine learning algorithm

“…These studies do not provide any quantitative methods to select a pilot area. In the second category, the reservoir area is filtered to select the pilot area according to some merit parameters [11][12][13]. These studies are based on reservoir past performance.…”

“…However, an area with moderate to good reservoir properties is another selection criterion. For example, having remaining oil saturation in the range of 0.2-0.5 could lead to an appropriate pilot area [11]. According to other studies [7,8], high remaining oil saturation has been applied to locate pilot areas.…”

“…For example, a pilot area could be selected based on the quality and quantity of the available petrophysical data [4,14,15]. In addition, less interaction between the pilot and production areas could lead to a more reliable interpretation of the gathered data [4,[11][12][13]. Besides, the closeness of the pilot to existing facilities could lead to economic aspects [12][13][14].…”

Optimization and comparison between polymer, surfactant-polymer and water flooding recoveries in a pre-salt carbonate reservoir considering uncertainties.

“…The St Joseph offshore field in Malaysia is another offshore ASP system project found in the literature (CHAI et al, 2011;DU et al, 2011). The pilot study was focused on reservoirs containing a medium gravity oil and a chemical injection using an already existing waterflooding project from which facilities could be reused.…”