During development of high pressure/high temperature (HP/HT) gas wells in Oman, clean-up operations that remove up to 10 tons of proppant fracture material from individual gas wells have become routine. The continuing development of fracturing, clean up and testing processes in the HP/HT well-testing environment has provided a unique opportunity to fulfill the need for enhancement of proppant clean-up equipment and methods.
Efforts have been concentrated on improving clean-up times, equipment efficiency and refining the design of the desander/filter sand management system (SMS). As a result of the improvements, the clean-up and testing processes have undergone significant modification.
During the initial phase of the project, numerous challenges had to be overcome, and improvements were made in the solids clean-up process. This paper will describe how proppant and other solids materials were managed during the wellbore and formation clean-out process.
The Oman LNG upstream project has developed the deep gas and condensate fields in central Oman. The project currently has a peak gas processing capacity of 40 million m3/day and an estimated peak condensate production of 12,500 m3/day. To obtain this capacity, 36 wells are being drilled in an initial phase over the first 2 1/2 years, with a potential project requirement of 130 wells. The wells are drilled vertically to the hydrocarbon-bearing sandstone formation at depths of between 4,200 and 4,700 m and completed with a 4 1/2-in. liner with 5-in. and 5 1/2-in. tubing. The reservoir pressure varies between 500 and 580 bar, and the temperature ranges from 125°C to 145°C. At present, the operational strategy is to hydraudically fracture all wells by means of up to five stacked proppant fractures using a ‘tip screen-out’ design to intercept as much of the 200-to 250-m reservoir height as possible. The wells must be cleaned up and tested to evaluate fracturing results and to obtain reservoir information prior to production.
To meet the start-up gas production targets, up to five rigs, two fracturing units, and two well-test units plus associated services were contracted. An integrated service contract covering cementing, fracturing, coiled tubing, perforating and well testing was awarded to enable and encourage contractor ownership for the entire scope of work.
The objectives of the system were to 1) reduce the time between tests and 2) assist the customer in achieving the target of delivering gas capacity of 40 million m3/day over a period of two years. To meet these parameters, two well test units are being used.