Terai and Siwaliks have been divided into 10 Exploration Blocks, each of approximately 5,000 sq.kms in area. These blocks were opened for bidding exploration acreage in 1985 for the first time (Figure 6).

Shell Nepal B.V. (1986-90) carried out exploration works in Nepal (Block 10) including geochemical study of seep samples. It has also acquired gravity and seismic survey (over 2,000 line km) in close grid pattern. The company had drilled an exploratory well (TD.3520m) to test the hydrocarbon potential of a seismically defined structure. The hole was dry and did not penetrate up to the basement. The result obtained from the drilling has created a valuable database for the exploration venture.

Since 1982-1992, over 5,000 km of multi-fold seismic data has been acquired. The field survey provides regional seismic coverage of most of the Terai and limited coverage in the Siwaliks (Figure 7). The data has been processed and interpreted by different seismic service agencies. A number of valuable geophysical interpretation reports are available in the Kathmandu Data Centre.