Publications

Proper choke valve selection for wellhead (later addressed as ‘choke’) sandy wells from the beginning can save millions of dollars. For example if after procurement found that choke are not sand resistance and need replacement, with field size as 1 field in Delta where new wells in minimum 40/year, cost for replacement would be 1.2MUSD for choke only (USD 30K/choke) and 1.6MUSD for piping modification (USD 40K for piping modification in swamp area). More years with wrong choke valves will accumulates number of wells requires correction. Delta Mahakam is a mature field with bottom-top perforation strategy. Recent wells have more possibility as sandy wells than before. Today 50% are sandy wells with increasing percentage. Depend on economical evaluation, various sand controls already been used to reduce risk, but nevertheless sand still being produced. Damages due to sand erosion are found at surface facilities, especially at wellhead choke. Choke is the first device to choke fluid pressure. Higher pressure drop across choke, higher fluid velocity travelling across choke. From record in the observed field, 85% of leak due to sand located in choke valves. Choke receives most severe sand erosion impact due to gas contaminated with sand flowing at sonic velocity. If eroded chokes not being replaced by proper ones, sand may penetrate choke bodies and cause hydrocarbon leak to environment. Obviously leak causes production loss. It may cause fatality as well, but unfortunately it never happens in Delta Mahakam. From last 10 years, from chokes which found eroded, around 10% were causing gas leak. This paper describes effort in Delta Mahakam to choose sand resistance choke based for sandy wells. Several choke technologies under observation are: fixed bean, multiple orifice disc, needle & seat, plug & cage, single orifice disc, and external sleeve type. Several key performances to be compared are: price, material strength and toughness, flow direction inside choke relate with jetting effect, width of operating range, maintenance cost, duration for maintenance, and trim design. Proper choke selection will lead to less shortfall due to shut down (for maintenance or due to accident) and OPEX efficiency for choke operation (less spare parts, longer service time duration, etc).