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.
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 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.
Electricity, pumps and rig time are the major costs associated with beam pump artificial lifting method in heavy crude oil.
In reducing operation costs, which are mainly associated with sand production, high viscosity, high GOR and rod flotation, Ma raven has successfully tested the progressive cavity pump in Bolivar Coast progressive cavity pump in Bolivar Coast fields.
The application of the method has reduced energy consumption over 60%, increased well production an average of 12% and reduced rig production an average of 12% and reduced rig activity sore than 40% in extraheavy and heavy type crude oils. This equipment was also tested in extraheavy oil slanted wells with excellent results.
The application of this method through an in house computer program has saved 10 million dollars/year in Maraven operational costs. It is expected to extend this program to other areas.
The Bolivar Coast fields are located in the east side of lake of Maracaibo. These fields are characterized by a variable viscosity crude (100 - 60000 cps) with gravity in the range of 9 deg. - 21 deg. API. The reservoir produces by depletion and compactation mechanism and is normally lifted by a conventional beam pumping system. Intensive activity is required to pull and run
plunger due to problems associated with the plunger due to problems associated with the high viscosity of the oil and sand content.
Numerous solutions to handle these production problems have been attempted with production problems have been attempted with various degree of success. The most prevalent remedies have been the use of heavy pony rod and gravel-pack completion, which increase the stroke of the travelling pump and reduce the influx of loose sand with adequately selected gravel held in place by screens.
Production problems attributed to high viscosity are broken rods and polish rod, pump and gear box damage by hitting, low pump and gear box damage by hitting, low production, etc. that normally cause production, etc. that normally cause premature hoist entry which considerably premature hoist entry which considerably increased production costs.
In order to reduce operating cost, alternative lifting methods were investigated. The progressive cavity pump being one of them. This equipment consist basically of a rotary type positive displacement pump driven by standard API sucker rods. A motor installed at the wellhead transmits the rotational movement to the subsurface pump.
The advantages of progresive cavity pump system are related to its capacity to move fluid continously, contrary to beam pump which produces only on up-stroke c.g. or one half the time. This results in better efficiency in handling sand and gas problems.
PROGRESSIVE CAVITY PUMP SYSTEM DESCRIPTION PROGRESSIVE CAVITY PUMP SYSTEM DESCRIPTION A diagram of the complete equipment is shown in Figure 1.