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Cairn Oil & Gas

Raageshwari Gas Terminal

Natural gas recovery- Zero Flaring During Milling Operations

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INTRODUCTION

RDG is Cairn India’s gas field in Rajasthan.

Tight gas reservoirs are hydraulically fractured to

increase recovery rates.

Plugs are installed in gas wells to isolate different sub

surface reservoir units.

In Raageshwari Deep Gas field development, 15 gas

wells were hydraulically fractured and later had plug

milling

During milling, metallic debris comes back on surface

with water, oil condensate and gas. Hence usually gas

can’t be taken straight in to production system.

Produced gas has to be flared.

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Problem Statement

Gas produced during milling is flared or burnt. Produced gas cannot be taken into production system due to presence of metallic

debris in flowback

Objective

ZERO FLARING DURING MILLING OPERATION

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Initial setup during millingFlowback - Sand + Hydrocarbon

Emergency shut down

GAS WELLChoke manifold to

control gas rate Production Header to Processing plant

On site condensate storage

Sand filter

3 phase separator

Waste water Pit

Gas flare ~ 8 MMscf1. Gas + Debris

2. Gas + proppant

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Challenges with initial setup

Estimated gas burnt/flared per well during this operation is 8 MMSCF.

Gas flaring – GHG emissions / Revenue Loss.

At the end of milling operation, the stored condensate is to be transferred from onsite storage tanks to production

facility that takes another 3-4 days.

Suboptimal use of associated resources during this transfer.

Un-stabilized Condensate handling issues.

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Debris catcher

3 phase separator

Sand filter

Emergency shut down

GAS WELLChoke manifold to

control gas rate Production Header to Processing plant

Final setup during millingFluids in system - metallic debris + Sand + Hydrocarbon

Waste water Pit

Zero flaring

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Road map for final setup:

Debris catcher was incorporated in setup to separate debris and proppant.

Detailed risk assessment carried out for the amended plan among all stakeholders.

Agreement to never bypass sand exclusion systems – debris catcher and sand filter to ensure clean gas.

Maintained the differential pressure across the test separator to allow the condensate flow into the production

header.

Amendment in SOP for handling surges back in production facility.

PSIT introduced in the final setup for additional process safety.

Frequent sampling ensured at well pad to check any presence of debris.

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Challenges faced and action taken

Challenge ActionBig chunks of cast iron generated during milling could have damaged production system.

Metallic debris

A high pressure vessel was used as debris catcher to separate debris by virtue of centrifugal and gravitational forces.

Debris catcher

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Pictures of zero flare set up

Coiled Tubing Unit engaged in bridge plug

milling in a gas well.

A debris catcher. Gas and condensate flowing into Production

facility.

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Achievements…..Established a new benchmark for future milling operations.

Cost

Overall Cost saving by Zero Flaring : ~ 0.96 MM USD.

Improved Utilization of heavy rental well services units : 30% rental savings.

Environment

Reduction in Environment pollution: 16088 Tons of CO2 Equivalent.

Reduce impact on community and bio-diversity.

Safety

Handling of light condensate is avoided.

Accomplished entire fracturing – milling campaign with zero HSE incident.

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Replicability & Repeatability

REPLICABILITY

Hydraulic fracturing in tight gas wells is a prevalent practice in oil and gas industry. The zero flare setup can serve as a role model to other oil and gas companies involved in similar operations.

REPEATIBILITY

Other companies can also use same set-up to conduct zero flaring milling operation.

LIMITATION

This technique might not be used during exploration phase of an oil and gas field as production facilities investments are not done at such early phases.

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Thank You