Essar Oil Ltd. is focusing on exploration and development of coalbed methane (CBM) assets in eastern India. The company has lined up a plan to drill 650 development wells to accelerate CBM production in the Raniganj East Block (RG East-CBM-2001/1) in Damodar Valley and more than 500 exploration wells in four other blocks—Rajmahal (Jharkhand state), Sohagpur Northeast (Madhya Pradesh), Talcher and Ib Valley (Odisha).

“Of the planned 650 wells in Raniganj, around 200 wells have been drilled. A new contract for [an] additional 100 wells [has been] awarded,” an Essar Oil spokesperson said.

The Indian company early this month awarded Greka Drilling Ltd. a contract to drill 100 wells in Raniganj East Block in next 12 months. Five GD75 rigs are being mobilized to drill the planned wells. The block, which covers 500 sq km (193 sq miles) in districts of Burdwan, Bankura and Birbhum in West Bengal, is estimated to have CBM reserves of about 28 Bcm (1 Tcf). The wells drilled so far are producing 220,000 scm/d (8.8 MMcf/d) of gas.

Raniganj Development Plan

In addition to drilling 650 development and production wells, the development plan for the Raniganj Block involves construction of eight group gathering stations (GGS) and one main compressor station (MCS) and laying of interconnecting and transportation pipeline network for gas production, collection and transportation and sale.

According to the plan, the wells would be drilled the target depth of up to 2,000 m (6,562 ft) in the identified areas of the Raniganj Block. The development cumulative production wells are to be drilled in clusters with each cluster comprising of 50 to 60 wells. They would target depth with a combination of low-capacity rigs for the surface section and higher-capacity rigs for the coal-bearing section.

The GGS have a planned capacity of .45 MMscm/d (16 MMcf/d) each, with the compressor station having a planned capacity 3 MMscm/d. Each GGS will be linked to the cluster of wells. The interconnecting and transportation pipeline network, with a diameter ranging from 4 in. to 18 in., will be laid down to evacuate the extracted CBM. The CBM generated during dewatering of coal seams will be separated from produced water and routed through pipelines to the GGS. Total estimated production of CBM from the proposed project is at 5 MMcm/d (177 MMcf/d). Each well is estimated to generate a peak production of 15,000 cm/d (530 Mcf/d).

Essar had drilled 12 core holes, 15 test wells and 58 pilot cumulative-production wells in the Raniganj East Block during the two phases of exploration to assess its potential methane reserves and prospects for their development.

The data collected from the exploration wells revealed that the Raniganj East Block has estimated total CBM reserves of 28 Bcm (993 Bcf). Global consultant Netherland, Sewell and Associates Inc. estimated that the Raniganj East Block has 2C contingent resources of 5.6 Bcm (201 Bcf) and best estimate prospective resources of 22 Bcm (792 Bcf).

A large part of the coal seams in the block are located at depths of 1,000 m (3,281 ft) to 1,700 m (5,577 ft). The Raniganj Basin is floored by Precambrian metamorphic rock and filled with Permian through recent sediments. The Upper Permian Raniganj Formation is above the Ironstone Shale and is composed of a succession of coal seams, carbonaceous shale and shale alternating with bands of medium- and coarse-grained sandstone.

The Raniganj Formation is the target for CBM production in the Raniganj East Block.

New Exploration Plans

Essar Oil is also working on plans to launch exploration works in the Rajmahal (RM-CBM-2005/III), Sohagpur Northeast (SP (NE)-CBM-2008/IV), Talcher (TL-CBM-2008/IV) and Ib Valley (IB-CBM-2008/IV) blocks.

The official said that Essar has taken up a plan to drill 133 exploratory wells in Rajmahal Block, which is 150 km (93 miles) away from Raniganj Block. As part of the Phase I program, it would undertake drilling of 30 core holes and three test wells in the CBM block area. In Phase II, the company plans to drill 20 pilot wells to a target depth of about 2,000 m (6,562 ft) within the block area to assess the commercially exploitable CBM reserves. The pilot wells will be drilled vertically in clusters with a gas-gathering facility provided for each cluster. In addition, four supporting wells will be drilled at each pilot well site to augment the production, depending on the strata formation and the land availability.

The Rajmahal Block, which covers 1,128 sq km (436 sq miles), is estimated to hold prospective resources of 133 Bcm (4.7 Tcf), according to a study prepared by Advanced Resources Inc. (ARI). There are eight to 10 coal seams at a depth ranging from 600 m (1,969 ft) to 1,000 m (3,281 ft). The coal has moderate permeability and a gas content of 3 cm (106 cf) per ton.

The Rajmahal coals below a cover of more than 300 m (984 ft) may become gas saturated and methane, according to the study. A coalseam gas block located to the east of allotted CSG block RM-CBM-2005/III has been designated in the trap covered areas.

Another plan involves drilling 153 exploratory wells in the Sohagpur Block (SP (NE)-CBM-2008/IV) in Madhya Pradesh. Phase 1 includes drilling 25 core holes and three test wells area as well as 25 pilot wells to a target depth of about 2,000 m (6,562 ft) within the block area to assess commercially exploitable CBM reserves. Four supporting wells will be drilled at each pilot well site to augment the production, depending on the strata formation and the land availability.

The Sohagpur Block, which covers 339 sq km (131 sq miles) in Sadol district of Madhya Pradesh, is estimated to hold CBM reserves of 17 Bcm (600 Bcf).

Essar Oil also has plans to dig 158 exploration wells in the Talcher Block and 128 in Ib Valley Block in coal-rich Odisha. In Phase 1, the company will drill 30 core holes and three test wells as well as 25 pilot wells to a target depth of about 2,000 m (6,562 ft) with four supporting wells for each pilot well in the Talcher Block area. Exploration work for Ib Valley includes making 25 core holes, three test wells and 20 pilot wells to a target depth also to a about 2,000 m (6,562 ft) with four supporting wells for each pilot well within the block area.

The Talcher and Ib Valley blocks are estimated to have CBM reserves of 74 Bcm (2.6 Tcf) and 31 Bcm (1.1 Tcf), respectively.

The official said Essar is targeting production of CBM from these four blocks in the next three years. Essar Oil, which has participating interest in 10 conventional oil and gas blocks in India and abroad, is aims to take a leading position in CBM production in India. The country is believed to hold an estimated 2.8 Tcm (92 Tcf) in CBM resources.