The speaker, Serena Che, is a senior geotechnical engineer at Geotechnical Consulting Group. She has worked with developer and contractor clients on energy, infrastructure and building projects in the UK and abroad.
She will present a case study involving HDD bores for cable landfall of an offshore windfarm, for which she was the on-site geotechnical engineer. During her site work, she contributed to overcoming several geotechnical and drilling-related challenges. She recently published and presented a paper related to her site work in the European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE 2024).
HDD is ideally suited to crossings beneath natural and man-made obstacles and offers substantial cost, safety and environmental benefits. Despite HDD’s wide use, there remain concerns regarding project risk in certain situations. Key to HDD success is good management of the drilling fluid and the avoidance of excessive mud loss.
Fundamental risks in HDD arise from pressure build-up in-bore leading to hydrofracturing of the ground, heave of the overburden and mud loss – either to formation, subsurface infrastructure or up to the surface. Poor cuttings transport is a main trigger for bore blockage, leading to potential hydro fracture and the manifestation of the hazards associated with these risks.
The risks associated with mud loss are most severe on projects like the wind farm, where drilling starts at a clifftop and descends to punchout in the seabed. In-bore pressures before punchout are elevated by the hydrostatic head of the drilling fluid from the clifftop entry pit.
Serena will discuss other geotechnical challenges encountered onsite, along with the analysis of rare annular pressure monitoring data which provided valuable insights into the behaviour of cuttings in the bore.
The lecture will include lessons learnt, recommendations to minimise the risks of hydro fracture and bore blockage, and advice to other young engineers interested in this field.
The lecture will be held on November 7 at the Institution of Civil Engineers, One Great George Street, Westminster, London SW1P 3AA. It will also be streamed
