nwosu chioma sylvia

BYCHIOMA SYLVIA NWOSU

09CN09881SEPLAT PETROLEUM DEVELOPMENT

COMPANY

WELL COMPLETIONS

• Well Completion Philosophy

• What is a Well Completion?

• Functions of a Well Completion

• Rig operations1. Okpohuru 6 overview2. Open hole logging/wellbore cleanup3. Running 9-5/8 casing4. Cementing casing5. Nippling down/up of BOP/ wellbore cleanup6. Wireline logging Challenges encountered Conclusions Recommendations

Outline

Well Completion Philosophy• After careful interpretation and consideration of

well test data (coring, logging etc), a decision is made whether to set production casing and complete the well or to plug and abandon it.

• Decision to abandon is made when the well is not capable to produce oil or gas in commercial quantities(economic limit).i.e. the production is less than the operating cost

• “Completing a well” means getting the well ready for production This principally involves preparing the bottom of the hole to the required specifications, running in the production tubing and it’s associated down hole tools.

What is a Well Completion?• What is a well completion it is a series of

connected tubulars, with instrumented sections (accessories) and valve system.

• Connecting the payzone to the surface facilities• Allowing control of reservoir pressures• Allow reservoir fluids to be produced in a

controlled manner.• Allow the introduction of fluids/solids to the

reservoir system

Functions of Well Completion

Okporhuru Field is situated in OML-38, in delta state.

Directional drilling was carried out with an inclination of 33(deviated well)

The measured depth of the well is 11350ft

The U3000 sand at (9305-9445ft) and V4000 sand at (10583-10948ft) are targeted

Cardinal drilling rig 201 with 2000 HP was used for the operation.

Okporhuru 6 overview

Okporhuru 6 overview

Wiper trip 13-3/8

Running 9-5/8 casing

Cementing 9-5/8 casing

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Nipple down BOP, install well head, nipple up BOP

Wellbore cleanup & displacement to filtered brine

Wireline logging

Open hole logging

Other processes continued after rig tour

Open hole logging (GR,RESISTIVITY,RESERVOIR CHACTERISATION INSTRUMENT) was carried out by baker Hughes

Gamma ray log is used discriminate potential reservoir rock from impermeable rocks

Resistivity logs is used to identify the hydrocarbon bearing zones

Reservoir characterization instrument is used to determine initial reservoir pressure

All the resistivity logs were in accurate after running three tools

The 13-3/8 was wiper tripped with a hole cleaner i.e a bit and a bull nose

Open hole logging/wellbore cleanup

305 9-5/8 Casings were drifted and tallied and the casing shoe and float collar (non return one way valves) were measured making a total of 11345ft in depth

A float shoe, float collar with joints of casing (2 to 4) in between (shoe track) was made up and run in hole using elevators and spider slips to shoe depth of 1345ft and rat hole of 5ft (11350ft)

the casings where run in hole above the shoe track with 33 rigid and 3 bow centralizers placed at accurate intervals to properly align the casings in the middle of the well.

Running casings

Cementing is done to hold casing in place and to prevent fluid migration between subsurface formations.

The slurry composes of water, cement and other additives

Slurry composition was calculated. this is a very critical part of cementing as the amount of slurry to be used, sacks of cement, barrels of water, barrels of displacement mud etc. is calculated

The cementing process was separated in two depths LEAD(depth with the center of gravity) and TAIL using different additives

Adding an excess of 25% incase of washout

Cementing the casing

CEMENT IN SHOE TRACK: = CEMENT IN RAT HOLE: = = 0.72bbls 25% EXCESS: (0.25) CEMENT IN ANNULUS TAIL: = : 25% EXCESS: (0.25) TOTAL FOR TAIL: 272.5+0.91+6.5= 280bbls of

slurry CEMENT IN ANNULUS LEAD: = : 25% EXCESS: (0.25)   SACKS OF CEMENT: SACKS OF TAIL: of cement SACKS OF HEAD: of cement

Cementing the casing II

MIX WATER: TAIL: LEAD:

DISPLACEMENT MUD VOLUME:

 NUMBER OF STROKES:

Cementing the casing III

100bbls x 9.2ppg of Oil based mud followed by 50bbls x 6.5ppg of base oil was pumped at 10bbl/min to clean the well and remove mud cake;

90bbls of 11ppg spacer was pumped in. The bottom plug which was already

attached to the cement head was dropped, the 50bbls x 11ppg Scavenger slurry for

lead was pumped followed by 280bbls x 15.8ppg tail slurry.

The top plug was dropped; slurry was displaced with 814bbs x 9.2 obm displacement mud.

The top plug bumped the bottom plug and there was a pressure spike of 1650psi

The cement was left to set.

Cementing the casing IV

The B.O.P was nippled down, the 9-5/8 slip and seal assembly was installed into the well head

the slip and seal assembly is used to firmly suspend the casing to the casing head spool

the BOP was nippled up, and the well was circulated with filtered brine

The bit and scraper was run in hole to remove mud cake and pulled out of hole.

Nippling down/up of BOP/ Wellbore cleanup

The log was carried out using a Reservoir Monitoring Tool (RPM), because of the inaccuracy in resistivity for the open hole log.

Carbon/Oxygen (C/O) and Pulsed Neutron Capture (PNC) measurements acquired with the RPM tool provide water saturation and the gas-oil-water contact.

PNC is mostly used to find gases, used to discriminate hydrocarbon-bearing from salt water bearing reservoirs.

The PNC logs where logged up at a minimum of two passes at 10ft/min between the different sand intervals from 11270ft to 8398ft.

C/O is used to measure the relative abundance of carbon to oxygen.

Wireline logging

4 passes of C/O was performed at 1.67ft/min at the different sand intervals between 11270ft to 8398ft,

It was noticed at the first interval while logging up sand 11151-11270 that drag was experienced therefore the complete four passes was taken before moving up to other sand intervals taking 2 passes each.

This operation took a total of 5daysCement Bond Logs (CBL) and Ultra

Sonic Imager Tool (USIT), was carried out to check if the cement bonded properly between the casing and the bore.

Wireline logging II

Challenges encountered Resistivity logs was inaccurate during the open hole logging

causing a downtime in well operations

The okporhuru 6 well has been the fastest completed well in SEPLAT with very little downtime.

Well operations were strictly conducted according to well program I learnt the basic well completion processes The company loved me and they approved I work with them on my

research work and are willing to take me back to work with them, they also paid me a lot for going to the rig.

The H.S.S.E personnel should be hands on deck throughout the rig operation

All personnel on the rig should be very alert and safety conscious

Conclusions

Recommendations

THE END