ADMA-OPCO Engineering Division has recently innovated a Subsea Cooling Scheme capable of rapidly cooling down the temperature of operating fluids even in high flow gas pipelines. The scheme can be inherent into the original pipeline design without adding any additional costs resulting in the elimination/ reduction of various major risks whenever temperature is a main contributor. The higher the temperature, the higher are the cost savings and risk eliminations/ reductions. ADMA-OPCO has already applied the scheme into the detailed design of one of its major gas projects resulting in extensive savings in addition to other numerous benefits relevant to risk reduction and operations. The subject paper describes the challenging process of identifying all risks associated with the first application of its kind. Not less challenging was the technical management of those identified risks to acceptable levels. In addition to above, the paper describes the concept of subsea cooling and what are the associated extensive benefits to the pipeline system design and operations. Moreover, how to technically adopt such scheme to various needs utilizing the knowledge captured from the pilot application in ADMA-OPCO Project. The paper also briefly describes typical constraints which would limit the application of such a scheme. Finally, the paper highlights potential future developments relevant to the concept/ scheme and what is deemed required for widening its applicability. IntroductionHigh Temperature (HT) Pipelines are one of the major challenges in the Oil & Gas Offshore Industry. High temperature fluids flowing through subsea pipelines develop and/ or escalate numerous failure risks of those pipelines. Typical examples of those risks are global buckling of subsea pipelines (lateral and upheaval buckling), excessive stresses in pipelines, excessive loading on terminals at hot ends, de-rating of the pipeline carbon steel material, higher rates of internal corrosion, lesser efficiency of Cathodic Protection (CP) systems in addition Moreover, if the fluid temperature is not adequately cooled down at the inlet of the processing end, then higher cooling capacity shall be required at the processing facilities. Numerous techniques have been developed by the industry for mitigating various risks associated with HT pipelines. Proper engineering would eliminate or reduce risks to an acceptable level on subsea pipelines by applying an optimized combination of available risk mitigation techniques. The Offshore industry has already taken very advanced steps in development of various mitigation techniques especially in the last decade. However, it is worth mentioning that mitigation techniques are usually associated with huge costs of implementation in addition to complexity in both the design verification and work execution. The innovative Subsea`Cooling Scheme causes a very rapid cooling down of the flowing fluid through enabling direct contact between the pipeline carbon steel surface and the sea water. Thus, having the pipeline itself...

On-bottom stability analysis of subsea cables is commonly carried out in accordance with the leading industry practice for subsea pipelines "DNV-RP-F109". Similar to pipelines, the analysis method typically used is F109's Generalized Lateral Stability Method. However, this method is considered to be overly conservative for small diameter cables in shallow water applications such as the Arabian Gulf. Consequently, costly additional stabilization measures such as vast quantities of concrete mattresses are normally required. Given the flexible nature of cables, dynamic on-bottom stability analysis is considered to be a rational approach for optimizing the stabilization requirements. Dynamic on-bottom stability analysis is a known approach for subsea pipelines; however, its application is normally limited to extreme cases of environmental conditions where concrete coating requirements exceed practical limits. Hence, ADMA-OPCO has initiated a study to develop an FE model for dynamic on-bottom stability analysis of subsea cables. The outcome of ADMA-OPCO's study demonstrated that dynamic on-bottom stability represents the best approach for achieving cost-effective stabilization solutions for subsea cables. Hence, it is envisioned to become the norm for on-bottom stability analysis of subsea cables. The key features of the FE model are presented as well as general guidance for dynamic on-bottom stability analysis of subsea cables.

1.0 Introduction ADMA-OPCO is the pioneering offshore Oil and Gas Producer in Abu Dhabi, UAE dating back to the 1950s. ADMA-OPCO operates more than 1500 km of sub sea pipeline network, built over the years as part of the progressive development in Umm Shaif and Zakum fields. ADMA-OPCO vision is to work effectively as one integrated team to produce hydrocarbons from offshore areas aspiring to excellence in all aspects of the business. This paper identifies ADMA-OPCO current key challenges being faced in and around existing developments, "Brownfields" considering the additional challenges imposed by the extensively busy oil & gas market. The paper is aiming to conclude and recommend best practices, key success parameters and lessons learnt which shall provide significant values to future projects of same nature. Conclusions and recommendations were extracted through professional coverage of ADMA-OPCO Water Injection Pipelines Replacement Projects started in year 2000 and are anticipated to be complete by 2015 in a phased manner. It is worth mentioning that all executed phases have been completed with great success, ahead of schedule and below allocated budget. 2.0 ADMA-OPCO Replacement Strategy 2.1 Main Objective of the Replacement Strategy Replacement of existing water injection pipeline systems in Zakum and Umm Shaif offshore fields to enhance the capacity of the current system and ensure un-interrupted safe supply of water injection.

Offshore Structures are typically designed with a target end of field life between 20 and 30 years. Many offshore Structures remain in service while exceeding their designed life which requires robust methods for evaluating and maintaining target risk levels through regular sub-sea inspections. Risk based inspection plans are generated based on strength and fatigue analysis (typically S-N based fatigue assessment) which involves a number of uncertainties which are inherent to the fatigue process. These uncertainties inevitably lead to inconsistencies between analysis predictions and the outcome of underwater inspections. Although the inspection findings are acknowledged, there is generally not much effort made to make use of the inspection findings to optimise future inspection plans. This paper applies reliability updating methods to optimise inspection plans (inspection intervals) using fatigue reliability based on the results of in-service inspections. This methodology forms part of the work requested by ADMA-OPCO during the customisation of Atkins Fleet Management System (FMS) for the application to their Offshore Structures fleets. It has been reviewed and adopted by ADMA-OPCO to replace existing qualitative methods. The methodology works towards optimising their inspection efforts and cost to maintain acceptable target risk levels. The methodology is based on evaluation of the SN fatigue reliability since the SN Curves are implemented in the fatigue design methods outlined in International Standards. A probabilistic model for fracture-based reliability calculation is developed by calibration of initial crack size to match SN based fatigue reliability. This model enables utilisation of the Bayesian updating techniques which allow incorporation of the inspection results in the calculations. Environmental data from Umm Shaif Field (ADMA-OPCO) have been utilised in the calculations along with fatigue design SN Curves from the API RP 2A international standard. The calculations target the acceptance probability of failure levels of a critical component (hotspot) with a target design life of 30 years. In the event that no fatigue cracks are identified through in-service underwater inspections, the existing inspection plans can be revised utilising the developed methodology to optimise the inspection intervals, leading to cost saving and optimisation of the inspection plan. Major in-service inspection campaigns have been executed by ADMA-OPCO where no fatigue cracks were identified. Other operators within the region have also concurred that no fatigue cracks were observed during in-service inspection campaigns, which indicate that the methodology proves effective in optimising inspection costs within the region.

Offshore structures usually experience many stages of alterations, modifications, load additions and strengthening work during its operational life to meet increased production plans and/or changes in process/safety philosophies. Significant load increases are likely accompanied with strengthening schemes to cater for such additions. Conventional design methods for assessing these modifications employ linear structural assessment that do not account for actual history of loading/strengthening. Conventional design practices and current design codes do not provide specific guidelines covering the effect of progressive loading and staged strengthening in a manner that ensures accurate distribution of loads into the supporting structural elements. This paper illustrates the benefits of employing progressive loading and staged strengthening over conventional approach. The benefits are highlighted through two case studies involving the Re-assessments of ADMA's Collector Separator Platform (CSP) and Bridge B5 connecting the CSP to Riser Platform. The assessment of these structures utilizing this innovative approach were carried out to demonstrate that these structures are meeting code (API WSD/ISO19902) compliance under the proposed additional loading.