High Rate Sour Gas Wells Solids Free Clean Out

Al-Ahmari, Abdulrahman Saeed (Saudi Aramco) | Uzcategui, Elio Antonio (Aramco) | Alsyed, Samih Masarrat (Saudi Aramco) | AlGhamdi, Abdulrahman (Saudi Aramco)


Saudi Arabia's first offshore high rate dry gas field has an over pressured reservoir. Successful pressure control during drilling required the use of barite in the water based drilling mud. Barite is very abrasive and is insoluble in any acid or solvent. Any barite left in the reservoir due to mud losses has to be produced back to surface after completing the wells. This cleanup is crucial for the safety and longevity of permanent facilities, especially when high rate gas wells are involved; due to the high rate of impact of any solids that may be produced with the gas. It is also critical to design the cleanup job carefully to ensure proper equipment and safety measures are taken to avoid washouts and related safety hazards.

To ensure solids free production from day one, a procedure was implemented and successfully executed during the development of this first offshore high rate high-pressure sour gas field. This was achieved by using the rig as a main support and complementing the safety with the incorporation of the selected Solids Management System. In addition to the proper equipment, a detailed cleanup procedure, which covered systematic production ramp up and defined solids free criteria, was implemented. The added value and safety from having the rig on location during well cleanups is the expertise to kill the well in case of any well control problems. So far, this well cleanup setup and program has been implemented on 14 wells on three platforms with minor erosion and no safety issues. One platform with five wells is already producing and is flowing trouble free. This paper will describe the details of the setup of the rig facilities to clean these barite laden fluids from the wells, and the solids control equipment used and the cleanup procedure.

Field Background
Saudi Arabia's first offshore nonassociated gas field is located in the Arabian Gulf at a depth of 50-60 meters, at a distance of about 100 km from Dhahran1,Fig. 1. The field was discovered in 2005. Full field development drilling was started in 2008 with the drilling of the first five well platforms and later paralleled with the drilling of another four platforms. By the end of 2011, drilling, completion, cleanup and surface hookup were completed on the first three out of five platforms in the field.

Production is from carbonate reservoir "K?? of the Permian Era with an average thickness of around 1,000 ft. The top of the reservoir is around 10,500 ft true vertical depth (TVD). Average reservoir pressure and temperature is 8,900 psi and 290 °F, respectively. Most of the wells are completed as 7?? monobore with a 7?? uncemented pre-perforated liner across the target reservoir, Fig. 2.

Drilling Challenges
Drilling of this over pressured reservoir came with its own challenges. The high-pressure reservoir warranted use of high weight drilling mud, which meant using barite laden mud to accomplish this task. The drilling problems were exacerbated by the fact that the "K?? reservoir is laying under a thief zone "J.?? Due to the challenges associated with drilling through both reservoirs before setting casing, it was decided to set the casing just above the "K?? reservoir. Due to the faulty nature of the target reservoir even then, drilling through the target "K?? reservoir resulted in sudden losses and hole stability problems.