Dirok Gas Field, Assam, India


The Dirok gas field is located in block AAP-ON-94/1 B in Tinsukia District of Assam, India, and lies in close proximity to Digboi. The field is operated by Hindustan Oil Exploration Company, (26.882%) for joint venture partners Oil India (44.086%) and Indian Oil Corporation (29.032%).

A production sharing contract for the block was signed in June 1998 and followed by the approval of the Dirok discovery in the block as commercial by the Ministry of Petroleum and Natural Gas.

Production from the gas field is scheduled to commence in Q4 2016. The Rs3.25bn ($54m) proposed development will encompass drilling of wells, installation of gas processing infrastructure and transport facilities. An additional $66,825 will be required to implement the environmental management plan.

The gas field is estimated to hold 11.88 million metric barrels of oil equivalent (mmboe) in proven and probable reserves as of March 2016.

Dirok gas field location, geology and discovery

Located in the Assam-Arakan basin, the field lies in the Schuppen thrust belt and covers approximately 350km². It is located near Digboi, Tinsukia, Margherita, Doom Dooma and Makum.

The field encompasses Naga, Margherita and Disang thrust zones and is composed of weathered sediment of sandstone. It also includes stones of Pliocene to Pleistocene age, and Surma group of rock sandstone, siltstone and mudstone of early to middle Miocene.

Exploration activity in the block started in November 2000, leading to the acquisition of 2D/3D seismic data in 2003. The Dirok field was discovered by drilling three exploratory and two appraisal wells, which confirmed the presence of multiple gas-bearing sands.

Dirok gas field development details

The proposed field development includes bringing the three existing wells (Dirok-1, Dirok-2 and Dirok-4) on stream, as well as drilling three new development and producer wells for hydrocarbons production. A new gas gathering station and a modular gas processing plant with a capacity of 20mmscfd of natural gas will also be set up as part of the proposed development.

Pipeline installation will comprise two parallel gas pipelines and a single gas pipeline. The gas processing plant will be set up in Golai, Bhorpowai near Digboi and will process the gas and condensate produced from Dirok field gas wells.

New and existing wells and the gas gathering station will be located 25km away from Digboi in Dirok tea estate under Kumarpatty Panchayat. The gas gathering station will cover approximately 0.6ha of land. It will include construction of civil foundation, erection of manifolds, flow line and valve network. A fire water tank will also be set up along with a fire pump.

Gas processing plant at Dirok gas field

The processing plant will be constructed on 6ha of agricultural land in the Golai village and will be located 16km from the gathering station.

The plant infrastructure will include control room, administration buildings and warehouse, as well as manifolds, vessels, tanks, pipings and associated valves. Mechanical structural work and instrumentation will also be completed as part of the processing plant.

"The gas field is estimated to hold 11.88 million metric barrels of oil equivalent (mmboe) in proven and probable reserves as of March 2016."

Machinery at the plant will include scraper receiver, test separator, inlet separator and filters. Other installed equipment will include heaters, concealed ground flaring system, metering arrangement and effluent treatment plant, in addition to supervisory control and data acquisition (SCADA), generators and fire detection system.

Pipeline details

A pair of 16km-long pipelines will supply the gas from the gathering station to the processing plant, while a 9km pipeline will connect the processing plant to the off-take location in Kusijan for the sale of processed gas.

The two pipelines, running between the gathering station and the processing plant, will comprise a high-pressure and a low-pressure pipeline with a diameter of 8in. The pipelines will be installed parallel to each other at a depth of 1m.

The pipeline connecting to the buyer's off-take location will lie parallel to Margherita-Deomali Road.

Key players involved

L&T Valves has been selected to provide high integrity pressure protection system (HIPPS) for the field development. The product is the first to be developed in India.

A $30m contract has been awarded to Expro to provide design, engineering, construction, transportation, installation and commissioning of a modular gas processing plant. A team to operate and maintain the plant will also be provided by Expro.

The field's environmental impact assessment was performed by SENES.