This paper details the continuous field application of an anti-agglomerant lowdosage hydrate inhibitor (AA-LDHI) for a deepwater Gulf of Mexico subseatieback with an unconventional projected production profile. Due to pumplimitations and projected production, as well as methanol-in-crudecontamination issues, thermodynamic hydrate inhibition was not suitable forthis new well. The chemical was first qualified by rocking cell performancetests, followed by a rigorous topsides trial on the host platform simulating AAinjection into the expected water production. AA injection began less than 24hours after the well was brought online using methanol. Several lessons werelearned regarding the application of AA at low water cuts. The chemical hasbeen successfully applied for more than one year with no significant effects onwater quality or hydrate events including during shut-ins.
This paper will provide the feasibility for continuous application of AA fromearly field life without water quality issues when reliance on methanol, athermodynamic hydrate inhibitor, wasn't viable. Field and lab data will bepresented to support the case for continuous application of AA chemical withoutthe traditional water quality issues associated with LDHIs. Field data willalso reveal important discoveries regarding the application of AA at low watercuts (<1%). The discovery of the behavior of AA at lower water cuts is asignificant contribution to the industry. Chemical phase partitioning must beconsidered in an oil-dominated system.
Offshore production of oil and gas face several challenges with flow assuranceand water separation. Natural gas hydrates are of particular concern whenoperating at reduced temperatures and elevated pressures. Under flowingconditions, hydrates can form and plug a flowline in a matter of minutes. Hydrate management strategies have often relied on chemical inhibition whenmechanical or operational methods are not cost effective or prudent. Conventional treatment options include the application of thermodynamic hydrateinhibitors, such as methanol or monoethylene glycol (MEG). Low dose hydrateinhibitors have also been employed as part of an effective hydrate managementstrategy (Kelland 2005). Anti-agglomerants, one class of LDHIs that have beenparticularly prominent in the Gulf of Mexico region, function by associatingwith an already formed hydrate crystal (Huo et al. 2001, York 2008). Thisassociation disrupts the growth process and causes the hydrate crystals tobecome oil wet. This creates a transportable hydrate slurry and preventsagglomeration and plugging from occurring.
The first applications for AAs in deepwater production were limited to shut-inand restart scenarios (Cowie et al. 2003). The benefits of AA application overthermodynamic inhibitors included
