The ROVDrill Mk.2 is a state-of-the-art seabed push sampling, rotary coring andin situ testing system designed for working in 2500m water depth and obtaininggeotechnical data to a depth of 120m below seabed. The system has beendeveloped as a geotechnical upgrade to two ROVDrill subsea robotic drillingsystems previously utilised in rotary coring mode in deep-water for the seabedmining industry. The paper considers the key design features of the current generation of subseadrill rigs and contrasts some of the key conceptual design differences betweenthem. A brief case study looking at the evolution of the ROVDrill Mk.2 rig ispresented including discussion of some of the technical upgrades and an outlineof its principal specifications. A number of benefits of seabed drilling are highlighted, with particular regardto working in deep water and harsh environments. With the elimination of humanexposure to pipe and tool handling risks, improved operational efficiency andsample quality and increased borehole depth accuracy, the development of seabedpush sampling, rotary coring and in situ testing systems are attractive to theoffshore site investigation market and a real alternative to traditional drillships. A Brief History of Subsea Drilling Technology Subsea drilling equipment began to appear in commercial use in the 1970's. Theearliest examples of these units were diver operated, marinized terrestrialsingle-shot rotary diamond core drilling rigs used for shallow rock coring forsurvey purposes. They also found application installing the small diameterpiles which are used to restrain and stabilize oil and gas pipelines in shallowwater zones with rocky seabeds, such as those found in the Persian Gulf and NWAustralia coastal oilfields. During the last 25 years or so, in step with the marine industry move to deeperwater beyond diver depths and taking advantage of increasingly standardized andsophisticated ROV control technology, subsea drill rigs have become remotelyoperated. Early examples remained as single-shot rotary coring systems, butmore capable rigs were developed initially for the deep-water scientific rockcoring research community. As the technology matured more sophisticated drillrig functionality was developed such as subsea pipe storage racks, iron-roughnecks/foot-clamps for pipe make/break, drill/grout mud pumps andcomplete monitoring and surveillance systems. Since 1996 a number of heavier duty subsea drill rigs have been built for usein the both geological research and commercial subsea geotechnical market. These units are of higher power (up to 150HP) and are capable of drillinglarger diameter bores (typically in the range 50mm to 75mm core diametercapability) and to greater depth (from 20m to over about 100m) than previousrigs. Systems targeting the geotechnical market additionally feature as aminimum push sampling (i.e. sampling of uncemented soils) and cone penetrationtesting (CPT) capabilities.

This paper discusses the use of ROV technology to enable conventional geotechnical site investigations to change focus. The move to deeper water, close proximity work and decommission works has meant that the integration of ROV technology and conventional geotechnical equipment has led to a greater variety of solutions that can be tailored to fit a client's needs. The paper will cover the application of this technology in some recent projects. These will cover a decommissioning project where investigations were required on drill cuttings that existed underneath an existing structure and also locations close to seabed infrastructure. By integration of a CPT (Cone Penetrometer Test) and sampling equipment on to an ROV it was possible to fly around the structure to investigate both environmental and geotechnical properties of the ground. It will also cover the utilization of a fully developed ROV drilling system for a variety of projects from shallow water wind farm sites to deepwater developments, proving the versatility and cost effectiveness of these solutions. In summary, results will be presented to demonstrate the next generation of site investigation tools and explain how, after years of traditional one size fits all solutions, new technology is enabling project teams to fine tune investigations. Utilizing a variety of working platforms makes geographically remote areas more accessible and economical to work. The use of new developments, utilizing industry standard testing and sampling solutions, with deployment systems, incorporating ROV technology, is changing the way site investigations can be performed. This enables a client-focused approach to offshore geotechnical site investigations in technically and geographically challenging environments. Introduction The fundamentals of offshore geotechnical site investigations have not changed for decades. There is a requirement to measure soil properties insitu via the Cone Penetration Test (CPTU) and to recover soil samples to enable the assessment of soil properties by means of testing within a soils laboratory. The procedures and requirements for performing these testing or sampling activities are prescriptively described in various International Standards that are well documented. What is driving change is the nature of the site investigations. As developments continue to move towards deeper water, more geographically remote areas and locations that already have significant existing subsea infrastructure, the traditional forms of investigation are not always the most practical, technically suitable or economic solutions. This has led to the adaptation of the traditional methods of sampling and testing of soils being integrated with ROV technologies to enable a flexible and often more cost effective solution. It should also be considered that in many of the applications that are now using ROV technology there is less manual intervention with operations happening at seabed and thus a much reduced HSE risk than conventional deck mounted drilling and testing operations.

Backfill is frequently required on small diameter, steel pipelines for thermal insulation as well as a measure to mitigate upheaval buckling. Current industry practice for mitigating upheaval buckling is to rock dump on susceptible sections of pipeline routes. This process can lead to excessive and unnecessary remedial costs due to conservatism in backfill parameters. Methods of increasing the download on pipelines will reduce or even eliminate the amount of rock dump required. Improvement of backfill material and optimisation of current upheaval buckling models provide a number of options for increasing pipeline uplift resistance. Coflexip Stena Offshore has undertaken extensive research into upheaval buckling of pipelines and has carried out associated studies into backfill improvement techniques. The research incorporated a full-scale laboratory-testing programme that assessed the uplift resistance behaviour of backfill soils and rock dump material. The backfill improvement study reviewed traditional land based ground improvement techniques and their potential transfer to subsea applications. Potential innovative solutions were identified. Improvement of backfill material and optimisation of upheaval buckling models will result in cost-effective solutions for the mitigation of upheaval buckling. Introduction Small diameter rigid steel pipelines are frequently used as in-field tiebacks to transport high pressure and high temperature hydrocarbons. Since the distances over which these tiebacks are placed are relatively short, in comparison to export pipelines, the problem of upheaval buckling can be a significant concern for pipeline designers, installation contractors and field operators alike. Measures to mitigate upheaval buckling typically consist of trenching and perhaps backfilling the pipelines. One purpose of backfill material is to provide download over the pipeline to resist the vertical forcesassociated with temperature and pressure induced upheaval buckling. In areas where the backfill cover is not of sufficient thickness to resist upheaval buckling, additional rock dump is typically placed over the pipeline. In cases of highly sensitive pipelines blanket rock dump is normally required. However, it should be noted that whilst trenching is often required to provide physical protection and perhaps also on-bottom stability, the additional of backfill and rock dump inevitably leads to increased cost. In order to reduce such costs and to fully understand the failure mechanisms associated with upheaval buckling and cyclic ratcheting, the Coflexip Stena Offshore Group (CSO), has undertaken extensive research and development programmes. This paper describes typical trenching and backfilling tools, summarises the findings of the detailed upheaval buckling research programmes and describes potential backfill improvement techniques, which have been investigated by CSO, that could be employed to improve the download provided to pipelines. Trenching Small diameter rigid pipelines are usually trenched by ploughs or ROV based jet-trenching tools. Each of these methods has benefits and restrictions with respect to reliably providing backfill cover for mitigating upheaval buckling. Ploughs Modern pipeline ploughs are capable of trenching rigid pipelines post-lay in all soil types and even rocks where they are weak or heavily fractured