With the increasingly stringent national environmental rules, waste produced in drilling and completion process is forbidden to be discharged into the Bohai Bay or reinjected into the formation. The current disposal method of drilling and completion waste in Bohai Oil field has some problems such as high cost, low efficiency and high HSE management and control risk. Faced with these problems, drilling and completion waste reutilization and zero discharge technology has been developed and applied in this region. In order to reutilize drilling and completion waste which include cuttings circulated from formation, wasted drilling and completion fluids, the following aspects are carried out: Firstly, drilling platform is upgraded to meet the zero discharge requirement: solid control system is modified, cuttings closed transfer system and cuttings treatment system are equipped on the platform to collect and dispose the waste. Meanwhile, recovery and disposal capacity to support different spud drilling are assessed: cuttings transport capacity is up to 15m3/h, which can meet the highest requirements of 12-1/4″ hole drilling when ROP is up to180m/h. Secondly, the well profile is downsized to reduce the production of cuttings, mud and other wastes from the root, which can also improve efficiency and yield cost. The field application shows that the amount of the waste has been reduced by 41.39%, 39.86% and 41.52% in first, second and third spud drilling, and average ROP is 35%, 28%, 42% higher than similar wells drilled before. Lastly, in drilling and completion fluids system optimization and reutilization aspects, environmentally friendly drilling and completion fluids with low solid content are developed. The experiment shows that the properties of the liquid phase after solid-liquid separation can be reused, and the solid phase with low water content is easy to pack and transport back to land. Drilling and completion waste reutilization and zero discharge technology introduced in this paper has been successfully applied in more than 40 wells, and the volume of waste drilling fluid is reduced by 80%, which is a trade-off between zero discharge and well construction cost. This technology can also be applied in other offshore oilfield which is inevitable as the environmental rules become more and more strict.
An offshore oil field in China was experiencing production challenges due to high water cut and low overall production. In order to boost production and address these challenges, adjacent reservoirs would need to be accessed and developed. Application of multilateral completion technology was considered the best method to achieve this, saving platform slots, increasing reservoir contact and keeling development cost low. An integrated solution was provided that allowed Technology Advancement Multilateral (TAML) Level#4 Multilateral Junctions with Gravel Packed Lateral sections, the first application of this type in China. The existing mainbore was temporarily isolated. Casing Exit was conducted at designated setting, and Hook Hanger TAML Level#4 Multilateral junction system was successfully installed and cemented. The horizontal Lateral bore was subsequently entered and gravel pack operations were successfully performed. Hydraulic integrity along well string is key to successful horizontal open hole gravel pack(OHGP). This TAML level#4 Multilateral completion design provided hydraulic integrity at junction during the whole OHGP process, the key to successful gravel pack. The mainbore can be restored as required. This paper concentrates on the technology utilized to successfully complete these wells. Multilateral and Gravel Pack equipment, challenges and solutions that were deployed to make this project a success are outlined. Three old wells in the field have applied this technology and have successfully improved production by 200m3/d. The wells give ability to selectively produce or comingle, allowing more flexibility with production. The introduction of Gravel Pack into the lateral affords greater sand control capabilities and ultimately assists overall production in well life. This application is now field proven with demonstrated production benefits and has potential for implementation in more developments in the region in future.
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