The multidisciplinary authors have summarized the results from the Autonomous Inflow Control Device (AICD) deployment in multiple oil fields, and presented it in this paper as a practice worth replication in a similar heavy oil environment, due its many benefits in optimizing field development. AICDs have been tested mainly in labs and controlled environments with few comprehensive field trials. This paper will form the basis for that which will add to the state of knowledge in the industry.
The AICD technology was piloted in few wells of these fields. It comprises of mechanical devices installed with the sand face completion, which react in real time to the properties of the flowing fluids, decreasing/delaying the water influx (or gas if it would be the case) from high productivity zones, promoting increased oil production from other compartments of the formation, therefore, equalizing the drawdown along the horizontal section of the well and performing a dynamic water shut-off operation. No cables are required, as the devices work on the basis of viscosity and density difference between the oil and the water.
The AICD-completed wells showed initial water cut in the range 1% to 2%. Which has reduced significantly in comparison to nearby analogues. The initial net oil rate resulted to be more than 2 times of the expected one, with an acceleration of ~10,000 bbls of net oil during the first month. After the initial production period, the technology is still delaying the aggressive water cut development usually observed in these fields, having provided 2 times the expected net oil rate during the first 3 months, with an acceleration of approximately 20,000 bbls of net oil over this period. It has been concluded that the application of the technology is successful and will be deployed as a baseline in all future horizontal wells drilled.
The predominant drilling challenge in Oman's southern fields is efficiently penetrating the thick conglomerate sediments. The sedimentary section is encountered at depths ranging between 2500–3400m and is approximately 700–900m thick. The hard conglomerate sections have UCS values that range between 12–30 kpsi. The formations’ rounded clasts, pebbles, and/or boulders are deposited in a fine grained matrix and make rollercone (RC) drilling difficult. The major dulling issue is early gauge row cutting structure degradation that requires multiple bits/trips to complete the 12 ¼" hole section.
Over the last two years, a series of iterative design changes and subsequent field tests have led to optimized tungsten carbide insert (TCI) geometry and strategic placement of 100% diamond enhanced heal row inserts. A new-type of insert and layout geometry has also enhanced shirttail protection. The ever improving TCI design has significantly extended cutting structure life and improved borehole quality. New carbide grades, tougher inner row inserts and an advanced twin elastomer sealing system that protects the bearing have all extended bit life in high WOB conditions.
The field derived design iteration process has consistently improved performance over the last 12 years. In 1999 a typical rollercone used in Oman's conglomerate fields had a life expectancy of 10–20 hours. Currently, the operator can expect a rollercone bit to provide sustained ROP for 110–120 hours drilling in these same fields. The improved bit and motor technology has optimized drilling the build sections and dramatically reduced cost/ft by an average of 40% over the past two years. This paper will examine the bit development/design, parameter selection and the science that led to a significant increase in conglomerate drilling efficiency. Finally, the authors will outline new durability and ROP benchmarks and discuss reduced rig-time and resulting cost savings.
Deep Water Disposal (DWD) project started in 1995 to process the main facility excess water output. A side-effect of this DWD injection into the shared Mehwis formation is a pressure support to the nearby fields, the impact of DWD rates can be seen clearly on measured pressures, where-initially before the start of DWD-the field was in depletion mode, after which the pressure stabilized after stable DWD rates. Similarly, recently the decline of nearby fields pressure can be noticed as a response to lower DWD rates. This study aims to evaluate the extent of the pressure support in nearby fields from DWD and the required disposal rate to maintain the desired pressures, and hence ultimately reclassify that part of deep-water disposal volume to water injection (WI), without sending the remainder water to shallow disposal site.
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