Post on 30-Apr-2020
transcript
© 2018 Vedanta Limited
Cairn Oil & Gas
Raageshwari Gas Terminal
Natural gas recovery- Zero Flaring During Milling Operations
© 2018 Vedanta Limited 2
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