The first application of hydraulic fracturing in the offshore Abu Dhabi was executed safely and successfully. This achievement will be a valuable foothold to expand the field development target toward more challenging reservoirs such as deep tight sand in this region. There were huge amount of operational difficulties to carry out this hydraulic fracturing due to various operational restrictions, limited data availability and high-pressure & high-temperature (HP/HT) condition. Finally, these difficulties were successfully overcome by an intensive designing study on well completion, surface equipment, and operation associated with hydraulic fracturing for a tight gas reservoir.In this paper (Part 2), the key factors that led this trial to the first successful hydraulic fracturing in the offshore Abu Dhabi are described against the difficulties from operational point of view such as well completion design, arrangement of fracturing and surface testing equipment and acquired lessons learnt. However hydraulic fracturing design optimization from subsurface point of view is discussed in the other paper described by Kuroda, et al. (2014) as Part 1. Well completion design and equipment arrangement were optimized to overcome an extremely wide range of pressure and temperature condition with multi stage fracturing. Fracturing and testing equipment of high specification were arranged on the limited space of both the off-shore jack up rig and the fracturing vessel, and then these well-prepared equipment contributed to safe and accurate operation. Acquired lessons learnt will contribute to other offshore tight-sand gas reservoirs development in the offshore Abu Dhabi. These outcomes will be especially applicable in this region to optimize offshore hydraulic fracturing for tight HP/HT reservoirs in order to enhance the well productivity and enable economical development of marginal fields.

Simultaneous Operation (SIMOPS) i.e. concurrent execution of two or more activities at the same time and place, which due to their interaction result in increased operational complexity and level of risk.While challenging existing practices, team has benchmarked Company practices with shareholders, other OPCOs and Service Providers. All the activities having major impact on Production/Injection shut down were captured. Industry standard risk management approach followed to assess all the risks associated with each individual activity. After reviewing all the hazards and safeguards in place, activities were declared as Permitted / Restricted /Not Permitted.In total 17 activities were reviewed, 11 activities assigned as ЉPermittedЉ, 4 activities as ЉRestrictedЉ and 2 activities remained ЉNot PermittedЉ under SIMOPS.By enhancing SIMOPS efficiency by 30%, expected 3 Million Barrels of additional Oil production per year and increased injection rates. Saving above 150 Million USD per year (using current oil price of 50$/bbl). Benefits will further magnify after full scale implementation of multiple SIMOPS per field and increased rig activities in future.Enhanced SIMOPS efficiency helped the Company to increase effective production capacity and achieve its sustained production assurance milestones without any compromise on safety and with no additional cost.

To maintain oil production at sustainable rates through minimizing the production loss factors, there was a need to investigate the feasibility of conducting SIMOPS on old wood, unprepared & un-equipped, high producing oil Well Head Towers (WHT). For this purpose, Management has formed a multi-disciplined team to investigate the possibility of allowing oil production & water injection operations while carrying out drilling/workover activity in a similar manner to that adopted for ZADCO oil WHTs. While SIMOPS has never been implemented on ADMA- OPCO WHTs for oil production, it was noted that water injection SIMOPS was already under implementation. The methodology adopted by the taskforce is as follows : re-visiting the risk assessment which constituted the basis for the current SIMOPS by ZADCO through ADMA-OPCO. Categorising & identifying the WHTs where SIMOPS can be implemented based on considerable incremental oil production level. Site verification of SIMOPS by ZADCO. Reviewing & amending the current SIMOPS procedures with the purpose of producing special procedure for ADMA-OPCO oil WHTs. Site verification visits to rigs carrying out SIMOPS were made where open discussions with rig personnel were held and equipment / systems were checked and tested. It was noted during the function test of the deluge system that the water supply by the injection facilities/system on the WHTs is satisfactory where as the back up water supply from the rig was ineffective. The risk assessment has shown that most hazards are assessed at ALARP or acceptable level except for the following: • Rig Collapse : Mitigation of the hazard is through the major improvements in NDC Systems (Management, Maintenance). • Dropped Objects : Mitigation through re-enforced Impact Protection on top of production facilities. • High Pressure Testing : Shut down production and depressurisation of service pipe works will constitute appropriate protection. The current SIMOPS procedures maintained in ADMA-OPCO's were reviewed and amended to reflect the required modification to allow for SIMOPS on ADMA-OPCO Towers. The SIMOPS procedure will require formal approval of Site Operating Authorities (Umm Al Shaif (US), Zakum (ZK)), both Asset Managers & the Drilling Manager.

Over the last several years, improved recovery, especially in depleted reservoirs, has prompted many research projects involving operators, service companies and academicians. Recent work on rock-brinehydrocarbon interactions has demonstrated that carefully designed low salinity water injection in carbonate reservoirs has the potential for enhancing oil recovery as much as 15% compared with conventional treated sea-water or produced water injection. The implementation of this step-changing technology requires studies carried out on in-situ condition cores. Ultra-low invasion drilling fluids must therefore be used during the coring process, to preserve the formation in its original state, without altering its fluids composition, water saturation or wettability properties. This paper outlines the philosophies and criteria brought to reservoir coring fluids design, development and application of an All-Oil synthetic-based coring fluid.An All-Oil coring fluid with ultra-low invasion characteristics was developed after extensive lab testing. The fluid properties were optimized based on reservoir properties and challenging bottomhole conditions, which are presented in this paper along with design criteria, fluid characteristics, fluid development methodology, benefits, benchmarks set initially and field application details. Excellent multi-segments collaboration and team work during core planning, fluid development work and on-site fluid maintenance to achieve planned parameters led to operational success and are described in the paper.For the first time in UAE, a major offshore operator cut the cores with ultra-low invasion All-Oil Coring Fluid, which provided excellent stability to coring parameters and performance. The cores were recovered, processed and preserved in as close in-situ condition as possible, eliminating water contamination and preserving the core integrity, all of which are the basic essentials to achieve successful specialised formation flooding studies leading to the EOR Project. 520 feet of cores were cut in the reservoir section over 9 runs, with 100% recovery of high quality and uncontaminated cores. The cores were slabbed, plugged, photographed, packed, waxed and preserved successfully on site for transportation to lab for flooding studies.The fluids' outstanding performance that helped in achieving the coring objectives in this new coring strategy are discussed in the paper and lessons learned are contrasted with conceptual design for future optimisation. Laboratory test results are also presented which formed the basis of a well planned field application.

To maintain oil production at sustainable rates through minimizing the production loss factors, there was a need to investigate the feasibility of conducting SIMOPS on old wood, unprepared & un-equipped, high producing oil Well Head Towers (WHT). For this purpose, Management has formed a multi-disciplined team to investigate the possibility of allowing oil production & water injection operations while carrying out drilling/workover activity in a similar manner to that adopted for ZADCO oil WHTs. While SIMOPS has never been implemented on ADMA-OPCO WHTs for oil production, it was noted that water injection SIMOPS was already under implementation. The methodology adopted by the taskforce is as follows: re-visiting the risk assessment which constituted the basis for the current SIMOPS by ZADCO through ADMA-OPCO. Categorising & identifying the WHTs where SIMOPS can be implemented based on considerable incremental oil production level. Site verification of SIMOPS by ZADCO. Reviewing & amending the current SIMOPS procedures with the purpose of producing special procedure for ADMA-OPCO oil WHTs. Site verification visits to rigs carrying out SIMOPS were made where open discussions with rig personnel were held and equipment / systems were checked and tested. It was noted during the function test of the deluge system that the water supply by the injection facilities/ system on the WHTs is satisfactory where as the back up water supply from the rig was ineffective. The risk assessment has shown that most hazards are assessed at ALARP or acceptable level except for the following: Rig Collapse :Mitigation of the hazard is through the major improvements in NDC Systems (Management, Maintenance).Dropped Objects :Mitigation through re-enforced Impact Protection on top of production facilities.High Pressure Testing :Shut down production and depressurisation of service pipe works will constitute appropriate protection. The current SIMOPS procedures maintained in ADMA-OPCO's were reviewed and amended to reflect the required modification to allow for SIMOPS on ADMA-OPCO Towers. The SIMOPS procedure will require formal approval of Site Operating Authorities (Umm Al Shaif (US), Zakum (ZK)), both Asset Managers & the Drilling Manager.