Effect of Indiscriminate Hydrocarbon Exploration on Possible Occurrence of Earthquake in some parts of Niger delta, Nigeria

Abstract

Seismic activities leading to tremors have been a subject of interest in geophysical survey. Here in, we reported the (seismic) tectonic activities of Langbodo field, an area where tremors have occurred in the Niger Delta, Nigeria. The seismic data used in this research work were analyzed using the CPillar® and the Plaxis 2D® seismic softwares. These softwares are based on sensitivity, probabilistic and finite element analyses. The variation in the depth of the exploration boreholes for the five identified locations, LCT A, LCT B, LCT C, LCT D and LCT E with respective values 7525 km, 7000 km, 8000 km, 7600 km and 9000 km showed the extent to which the underlying crust can be pressurized. The seismic information from the drilled wells revealed that the tensional force created through stress ranges from 5.517 × 10^13 N to 6.130 × 10^14 N and that of compression ranges from 3.065 × 10^14 N to 5 517 × 10^14 N. The tectonic activities of each of the locations were recorded using the seismic reflection method. This study revealed that more than 50 % of the earth tremors experienced in the area were humanly triggered. Seismic records of the areas showed that human activities that result to rapid injection of fluid into the plates, if not controlled, can trigger tremors. The magnitudes of tremors that have occurred in the five identified locations LCT A, LCT B, LCT C, LCT D and LCT E are respectively 3.50 ML, 3.20 ML, 4.20 ML, 4.00 ML and 4.32 ML. This research work however concluded that the study area is likely to witness earthquakes of about 7.0 ML magnitude should explorations continue indiscriminately. Probable occurrence of earthquakes in this location can be nipped in the bud by setting up agencies that monitor and assess subsurface pressures, quantities of injected fluid, volume of extracted fluid, and the seismicity of vulnerable regions with time.

Keywords

• seismic activities
• seismic wave velocity
• depth of borehole
• compressional and tensional forces
• seismic reflection method