Gas Lift Redesign in Dual Strings Completion Wahyu Jatmiko ( BP-Indonesia ) Herry Subekti ( BP-Indonesia ) Gatut Widianoko ( Weatherford ) Presented by Henry Nickens, BP-America, Houston Title slide Keep the title brief and to one line? The second line (in smaller type style) is for the date of the presentation – depending on your presentation, you may also need to include Location and/or Presenter’s name/s and Job title if needed – as a such a second line may be used for these purposes. Do not include unnecessary information in your presentation title – starting off with clear and simple messages will set the style and focus the audience for what is to follow.

Gas Lift Redesign : To change setting pressure and port size of gas lift valves, unloading and operating valves, at existing mandrels.

BP West Java Well Work Perforation Sand Clean Out Matrix Stim WSO Scale Clean Out WSO Gas Lift Choke Opt Zone Change

West Java Field Overview West Java Reservoir Overview West Java Dual Completion Why redesign gas lift Process flow to redesign gas lift valves Summary

West Java Overview BP-West Java area is located offshore of the north of Java Island in Indonesia. Initial oil production was in 1971. West Java field covers an area of some 18,000 square-kilometers with total wells around 700. 75% of total wells are producing under gas lift system. Current production rate of 40,000 BOPD and 300 MMscfd of gas (~ 75 bopd/600 Mscfd per well) Colour usage A custom slide colour scheme has been applied

West Java Reservoir Overview shallow gas LL- 32 LL- 33/35 LL- 37 LL- 39 LL- 40 LL- 41 LL- 44 Cisubuh shales Pre-Parigi Parigi Limestone Main Massive Batu Raja Limestone Talang-Akar LL- 57 to LL- 64 Basement -1,000 ft -2,000 ft -3,000 ft -4,000 ft -5,000 ft -6,000 ft West Java reservoir is multi stacked sandstone and carbonate reservoir. Mostly oil was producing from main, massive, baturaja and talang akar formation. The rest of formation are gas producing. Liquid productivity index is 1-5 bbl/day/psia, average TGOR of 500-1000 scf/stb and current liquid production about 500-1000 BLPD. No reservoir pressure maintenance

West Java Dual Completion Dual completion was selected to : optimise oil production avoid cross flow be able to allocate production data perform well work do reservoir monitoring

Why redesign gas lift valves Periodically gas lift valve design is needed to : maintain liquid production due to declining reservoir pressure. response to the change of gas lift source pressure. increase gas injection rate due to increasing water cut. solve gas lift robbing problem Liquid production keep declining GLV redesign was done

Process flow to redesign Survey current gas lift performance Obtain field and reservoir data Matching well test to estimate - gas oil ratio - productivity index Redesign for best point of injection, setting valve pressure Optimize injection rate on short and long string

Process flow to redesign Survey current gas lift performance Gas lift gradient survey should be done prior to redesign gas lift to make sure there is no leaking in the tubing and to check gas lift performance. Dummy valves are leaking (~ 20% of wells)

Process flow to redesign Field and Reservoir Data To redesign gas lift, the following data is required : Current reservoir pressure data Flowing gradient survey Well test data Latest gas lift valves report Setting pressure report Productivity Index Latest gas oil ratio

Process flow to redesign Matching well test Stable well test is selected for well test matching. For the dual completion, well test data does not give gas lift injection rate data.

Process flow to redesign Matching well test To estimate productivity index, well modeling is built using nodal analysis with the input : total liquid water cut flowing tubing pressure total GLR reservoir pressure Injection rate estimated from Qgas,inj = Qgas,total – GORform x Qoil Sensitivity on productivity index is performed to match liquid rate with well test.

Process flow to redesign Matching well test Productivity index from well test matching is used to estimate gas oil ratio. If GORform not available, then sensitivity on GLR until no intersection between IPR and tubing hydraulic was reached. Then, current gas oil ratio could be calculated based on the result of the GLR sensitivity. Gas liquid ratio with no intersection, GOR = GLR*Liquid/oil

Process flow to redesign Design best point injection and setting pressure Optimum injection rate Short Long Once productivity index and gas oil ratio could be estimated, the gas lift curve is generated to determine optimum gas injection rate.

Process flow to redesign Design best point injection and setting pressure

Process flow to redesign Design best point injection and setting pressure

Process flow to redesign Dual strings gas lift injection rate optimisation Spreadsheet to check valve performance after new design is installed.

Process flow to redesign Case I (operating valve depth and flowing tubing pressure are similar ) Gas robbing potentially occur To avoid gas robbing use similar port size

Process flow to redesign Case II (operating valve depth and flowing tubing pressure are not similar ) Gas robbing potentially occur Use different port size to avoid gas robbing

Process flow to redesign Example Redesign Result

Process flow to redesign Example Well Test after and before gas lift redesign Target: 6 redesigns/month Production ~ 80 bopd increase Injection Gas ~ 200 mscf/d decrease

Summary Uncertainty on gas lift injection rate each string, current gas oil ratio and productivity index in dual strings completion could be estimated using nodal analysis. It is difficult to reach optimum gas lift injection rate in both string as gas injection rate in both string should be balance. Gas lift robbing is the main problem in dual completion but it could be avoided by: using similar port size in both string when flowing tubing pressure and operating injection point depth are similar. using different port size between short and long strings when flowing tubing pressure is different. Ideally, gas lift gradient survey is performed regularly to prevent gas lift robbing.

Contact for further information: Wahyu Jatmiko wahyuj@bp.com