Continuous Incremental Reserves in an Oil Rim Marginal Field Development through Integrated Technical Initiatives and Technology Advancements
Authors: Masoudi Rahim , Karkooti Hooman , Chan Keng S. , Othman Mohamad B. , Altunbay M. Mehmet 
Published: March 2015

Oil rim reservoirs are commonly marginal reserves with challenging drive-systems with high development cost and, therefore, are commercially less attractive. Development evaluation of such complex fields with the conventional methodologies and technologies may result in unsuccessful scenarios. The studied field, located in offshore Peninsula Malaysia, is a marginal oil rim reservoir with the oil column less than 42 ft with limited oil-in-place. The field was initially evaluated as a challenging development and a non-commercial asset. However, the integration of various technical initiatives and applying new interpretive techniques turned the field into an attractive asset and reserves have been continuously upgraded since the field development started.

The field was undergone proactive phasing development and reservoir management with a fit-for-purpose monitoring plan. The development strategy with long horizontal wells (i.e., up to 2 km) and smart completion with inflow control devices was matured through the development phasing and well-by-well performance evaluation. Various tracer applications with the PLT campaign in the long horizontal wells pre/post water-breakthrough (WBT) were used to justify the long horizontal wells. Well placements relative to contact were progressively improved allowing the delay in WBT and increasing the RF. Production rate, draw-down and GI/GP were continuously optimized pre/post water/gas break-through. Simulation model incorporated robust modeling of flow dynamics of the oil intervals in the capillary transition zone and long horizontal wells with smart completion modeling using the segmented well approach.

The applied development strategies together with the proactive reservoir management made the field development as a record successful case in Malaysia. The recovery factor progressively increased from earlier 16% to 35% presently. In this paper, suggested workflow, guidelines and key tasks with the field data and the results are presented and discussed for the studied field.

Introduction

The field is located approximately 260 km northeast of Terengganu, Peninsular Malaysia. This field consists of structurally stacked, areally spread-out, shallow sands that are poorly consolidated with permeabilities in the range of Darcies. The target reservoir has a 42-ft of 23° API oil column overlain by an associated gas cap and underlain by extensive aquifer with initially unknown drive-strength. In this field, oil is speculated to have been displaced by imbibition process over geological time following the initial primary drainage to create both a Displaced Oil Zone (DOZ) and a Capillary Transition Zone (CTZ) over the full length of the oil column (Fig. 1).

Understanding the CTZ, DOZ, correct flow dynamics, saturation and mobile oil/water distributions can greatly influence the resource estimation, field development/planning and the ultimate recovery. The field background, capillary transition zone characterization and modeling concepts for the studied field were detailed in earlier publications [1, 2].