HORIZONTAL WELL LENGTH OPTIMIZATION FOR A SOUTH OMAN FIELD

ABSTRACT

Oman produces around 850,000 bbl/day of crude oil from around 85 fields of which 35% comes from horizontal wells. Horizontal drilling was started in 1986 with three short radius wells drilled in chalky oil reservoirs due to gas or water coning and low production rates. Results were not sufficiently encouraging to lead to future activity in the short term. Horizontal drilling technology evolved rapidly and in 1990, Oman embarked on a more ambitious program. The results, this time, were so impressive that the trial was extended and has led to almost continuous horizontal drilling. Some 100 horizontal wells per year are expected to be drilled for the foreseeable future. These wells exploit both clastic and carbonate reservoirs from Precambrian to Cretaceous age, thin and thick oil columns, light and heavy oil, and a wide range of reservoir quality.

Multilateral drilling in Oman has also shown significant benefits in increased production rates, reduced costs and increased oil recovery from existing producing fields and previously uncommercial oil accumulations. Well costs have been reduced by optimising the well design and drilling operations. The most significant cost saving has been due to a reduction in hole size and casing scheme.

The main focus of this project is optimizing oil recovery in a South Oman oil field using multilateral well technology. It mainly outlines both the effects of horizontal length and number of horizontal legs completed for different reservoir properties using Eclipse 100 black-oil simulator as a numerical tool.

Eclipse black-oil simulator is utilized in order to formulate the reservoir models of the concerned field and two other synthetic reservoirs having different rock properties. In order to generalize the findings, correlations are developed for different rock properties. That way predictions for optimum well conditions for any particular field in Oman could be established.