ABSTRACT
An engineering evaluation was conducted to determine development feasibility of a heavy oil prospect located in the UK sector of the North Sea in 348 ft of water. The reservoir is located at approximately 3,000 ft. The matrix is highly unconsolidated and contains crude oil with a viscosity of 132 cps at reservoir conditions. In addition, the oil column is underlain and in direct contact with a large water zone.
The paper presents a procedure to evaluate a potential offshore field. The procedure uses reservoir, drilling, and operations engineering technology in developing a screening technique to determine how to proceed with evaluating the development.
Simulation was used to evaluate reservoir performance under depletion drive, natural influx, and water flood. Thermal and non-thermal enhanced oil recovery (EOR) methods were evaluated using analytical techniques. Results of the simulation and analytical techniques are presented. Results of sensitivity studies to determine the effect of aquifer strength, vertical communication, and production rate on ultimate recovery of the high viscosity oil are also presented. The impact of horizontal wellbores on ultimate recovery was determined by simulation. The effect of vertical location of the wellbore within the reservoir and wellbore length were modelled and results are presented.
Work required on the directional drilling and well test programs for the exploratory wells to evaluate the shallow, unconsolidated reservoir are discussed. The technique of drilling the proposed multiple drainhole wells is reviewed.
Production Systems Optimisation (PSO) was used to evaluate factors not normally considered in reservoir simulation. PSO is an analytical tool to calculate pressure losses as a function of rate from the reservoir to the stock tank. The objective of the analysis is to economically design the most efficient production system over the life of the well. Formulas used in the technique which are applicable to other fields are presented in the paper. The effect of pipe diameter, gravel pack permeability, and screen diameter on production rates are discussed. The effect of water production is also included.
