Development and Qualification of a High Angle Multi-Frac (HAMF) Completion System for Deepwater Subsea Wells

Abstract

Deepwater developments in the Gulf of Mexico have historically focused on high kH (∼10,000 – 100,000 md-ft) Miocene reservoirs. Production from a single sand in these prolific reservoirs has been sufficient to justify the high costs of a deepwater well. In the last decade, there have been significant volumes discovered in Upper/Lower Wilcox age reservoirs in the Gulf of Mexico. These new discoveries typically comprise of stacked sets of lower permeability (1 – 20 md) sandstones. Several of these Wilcox discoveries have been successfully developed using cased hole vertical wells and single trip multi-zone frac-pack completion systems. Despite some of the successes, the project economics of vertical fractured wells in the lower Wilcox remains challenging due to low recovery factors (8 – 20%) and low EUR/layer. This paper describes an alternative lower completion concept for developing these lower Wilcox reservoirs referred to as a High Angle Multi Fractured (HAMF) well design concept. The value of the HAMF concept was assessed via reservoir modeling to understand it's value for low mobility reservoirs. Supporting evidence on the EUR uplift from analogue field studies and analytical modeling is also shown. Functional specifications for the completion system and the frac sleeve were developed based on the reservoir and operational requirements for subsea installations. Following design reviews, a completion system was selected that met the requirements, albeit with some modifications. The selected sleeve system was designed, manufactured, and went through comprehensive qualification and testing. A horizontal cemented 10 sleeve system was installed and hydraulically fractured in a land trial to evaluate the system functionality. Diagnostic evaluation including downhole gauges, radio-active tracers and 3D acoustic imaging are presented.