India’s state-run ONGC Ltd. is preparing to launch an integrated development plan for gas fields in two adjacent shallow-water blocks—KG-OSN-2004/1 and GS-49-2—in the Bay of Bengal.

Many of the gas fields are “marginal and economically not viable on a standalone development basis,” a senior ONGC official said.

The plan involves drilling and completing seven new wells in KG-OSN-2004/1 and two new wells in GS-49-2. The seven wells in KG Block (AL-1-A, SA-1-A, SA-1-B, NL-2-A, NL-3-A, NL-3-B and CS-1-A) will be drilled at water depths of 16 m to 140 m (52 ft to 459 ft) with cased-hole gravel pack completion, while two wells in GS Block (GS-49-2/1 and GS-49-2/2) will be developed at a water depth of 7 m (23 ft) with dual packer and dual string completions with 2⅞ tubing.

The plan also includes building five unmanned production platforms (SA-1A, SA-1B, NANL-2A, AL-1A and NANL-3A) in the KG Block and one (GS-49-2) in the GS Block.

Seven wells will be tied with five platforms in the KG Block, and two wells will be tied with one platform in GS. The produced well fluid from SA-1A WHP will flow to SA-1B. Combined, the fluids will move to NANL-2A WHP and onto NANL-3A.

Two subsea wells, CS-1-A and NL-3-B, will be tied with AL-1A WHP through a loop line, and the produced fluid will flow to the centralized NANL-3A. Production from GS-49-2 WHP will be pumped to the centralized platform.

Five flowline segments of 8 in., two segments of 12 in. and one 10-in. segment—with a cumulative length of 47 km (29 miles)—will be developed between the platforms.

In addition to accommodating the risers of incoming and outgoing pipelines, the substructure of the AL-1A platform will make way for the I/J tube to accommodate umbilical for the subsea wells. Furthermore, each NANL-2A, SA-1A, SA-1B and GS-49-2 platform will be designed to accommodate one future riser of 8 in. The AL-1A and NANL-3A platforms will be designed to accommodate two 12 in. future risers.

The subsea pipeline from the centralized NANL-3A platform will be tied to a new onshore facility at Mori/Odalarevu, with capacity of 8 million metric standard cubic meters per day of gas.

“Development of [the] KG-OSN-2004/1 Block along with GS-49 has a total production potential of 6.4 MMcm/d [226 MMcf/d] of gas with nine producers to deliver a cumulative gas production of about 14.14 Bcm [499 Bcf] over a period of 16 years,” the operator said in a report.

The integrated development plan is estimated to cost about $500 million.

During the exploration stage, ONGC drilled nine wells in KG-OSN-2004/2 Block, out of which five were discovery wells—CS#1, AL#1, SA#1, NANL#2 and NANL#1. One well NANL#3 established the extension of CS#1 pay to the north, and the NAMA#1 well had gas indications. The NARV#1 and NANL#4 wells were dry. The CS#1 channel is believed to extend south. The block is spread across 1,131 sq km (437 sq miles) at a water depth of up to 350 m (1,148 ft) in the Bay of Bengal.

In the GS-49-2 Block, the operator discovered gas prospects in one of the two exploration wells. GS-49-2, the second well drilled on the structure on the southwestern culmination, encountered multistack reservoirs.

In addition, ONGC is looking to build an onshore facility near the landfall point at Mori or Odalarevu on Andhra coast to process the collected fluids from centralized NANL-3A platform. The well fluid gathered at NANL-3A will be transported to the Mori onshore facility through an 18-in. by 20-km (12.4-mile) flowline.

—Ravi Prasad