Geological Engineering for Hazard Assessment of Pad AWI-14, Salak Field, West Java, Indonesia

Abstract

Locally steep slopes within the Salak geothermal field yield the possibility for large-scale landslides. During the heavy rains of 2003 Salak recorded significant slides that caused major damage and shut down a part of Salak operations for 3 months. Over the period 2010-2011 several new landslides have been identified around the Awi-14 injection location. The landslides have significantly impacted surface facilities including a pipeline, road, and well pad, and have the potential to impact injection strategy within Salak field. The main contributing factors to the landslides in the area threatening the Awi-2 to Awi-14 pipeline were the steep slopes, high rainfall, and high porosity, loosely consolidated near-surface rocks. During periods of heavy rain the soil has the tendency to become over-saturated with water, triggering slope failure that can lead to soil creep or landslide depending on the nature of the underlying soil. Several geotechnical analyses have been applied in 2011 to solve those problems, including shallow drilling for soil investigations, geological engineering mapping, geophysics survey, and finite element slope stability modeling. Those methods have helped to identified landslide mechanisms around the pad, quantify the risks at identified critical areas, provided recommendations for cost effective mitigation measures. Design and installation of both temporary and permanent landslide mitigation measures such as geo-textile, gabion baskets, bore pile / sheet pile, drainage systems were done to prevent occurrence of further landslides and restore the stability and viability of Awi-14 as an injection well in the Salak field.