Integrating geophysical exploration methods to minimise environmental impacts: A case study of oil and gas exploration, exploration area 2 Albertine Graben, Uganda.

Abstract

Geophysical exploration techniques for oil and gas are vital in providing information on subsurface bedrock structures, and sometimes, lithology and hydrocarbon indications thereby pinpointing the probable location of hydrocarbons which in turn guides the drilling location. The exploration techniques impact the environment both positively and negatively. The Albertine Graben (AG) is ecologically sensitive and a potential hydrocarbon province, but the knowledge gap identified is a lack of a template to acquire good quality data with minimal environmental risks. Geophysical exploration methods are categorized into passive and active. Passive methods monitor changes in the earth’s field (such as gravitational and magnetic fields) known as potential field methods, while active methods involve the introduction of external energy into the subsurface the earth’s response is monitored in turn, such methods include seismic reflection and refraction methods. This research explored the possibility and means of acquiring the required geophysical data quality with minimal environmental impacts. Initial exploration could begin with satellite imagery for a broad scale identification of topography, geological structures, the potential field methods follow up to show basement depth and shape, basin extent and thickness, then FTG to show structural trends and then targeted seismic to pinpoint drillable prospects. Environmental risk assessments for the exploration methods were carried out using the HAZiD method based on the AS/NZS ISO 31000: 2009, and the ALARP risk management tool, data resolution attained from the different geophysical Exploration methods was compared. The environmental risks were compared too in ascertaining the possibility to acquire required resolution with minimal environmental impacts. Airborne geophysics had minimal (low) risk, a broad scale resolution that may not be conclusive enough to pinpoint drillable spots. On the other hand seismic has the best resolution to pinpoint drillable spots but the method can have adverse impacts if not properly planned