The following 3 methods may be used in performing a squeeze cementation: Spot and Squeeze, Straight Squeeze and Circulation Squeeze.

1. The Spot and Squeeze or Block Squeeze method is the term used when cement is spotted over the required interval and the squeeze pressure is applied afterwards in order to force or “squeeze” the cement slurry in the pore space of the formation.

2. The Straight Squeeze method describes the technique where the cement is spotted and squeezed directly into the formation. This method must be used if injection rates are low (Hesitation squeeze).

3. A Circulation Squeeze should be used when cement behind casing is shown to be poorly bonded in places where it is required for zonal isolation and the judgement is made that circulation may be possible. The casing is perforated in two places, a packer is set between the perforations and cement is circulated through the annular space between casing and the formation.

Note: Perforation reference is from CBL/VDL

General Guidelines

• If an attempt is to be made to squeeze cement into perforations or into a casing leak etc., and the cement opposite the place of squeeze is to be drilled out later, injection rates should be established before cement is squeezed. This should be done using a solids free fluid eg., water or brine. Acid may be spotted ahead of a squeeze job to break up plugging mud particles. Reference shall be made to the Cementing Contractor for the acid recipe.
• Establishment of the injection rate is less important if the well is to be abandoned and cement will not be drilled out afterwards.
• High squeeze pressures which may induce formation breakdown must be avoided, particularly in the vicinity of faults and stacked reservoirs, in order to prevent zonal communication via vertical fissures. The formation closure pressure should never be exceeded, unless specific written orders to do so are issued by Head of Drilling Operations.
• When a packer has been set just above the perforations or zone to be squeezed off, the bottom hole pressure must be kept below 80 % of the collapse pressure of the weakest casing in use. Changing the setting point of the packer or applying back pressure may help to increase the allowable squeeze pressure.
• Annular back pressure should be applied in all cases having a differential pressure across the packer greater than 1 500 psi.
• The hesitation squeeze technique should be used in lost circulation / high pressure zones to aid bridging of the cement solids.
• The simplest way to carry out a squeeze is to spot the cement and squeeze it by applying pressure while the annulus is kept closed. However, a packer must be used if the pressure during the squeeze will exceed the maximum allowable pressure at any point above the planned depth of the cementation.

The following guidelines should be used for determining the type of packer to be used:

• The Spot and Squeeze technique is only possible using a retrievable packer.
• If the well is to be abandoned a cement retainer should be used, since it will form an additional mechanical seal and for reasons of cost.

Requirements

• A consistent slurry gradient is particularly important in the case of (small) cement plugs. The cement must be batch mixed or dumped until the correct gradient is achieved.
• Thin slurries with low fluid loss of less than 50 ml/30 min are used for regular squeeze cementing jobs, to reduce premature slurry dehydration during placement.
• Thixotropic cement slurries may be used in zones where losses are encountered.
• Slurries designed for use in remedial cementation operations, will be formulated such that:

Pumpability Time = Mixing Time + Slurry Displacement Time + Circulating Out Time + 60 mins (Safety margin)

The laboratory will allow for the higher pressures applied.

Preparations

• In deviated wells with less than 30° hole angle, a viscous pill of approximately

  100 ft length can be used as a bottom for the cement.

• If there are any perforations below that need to be protected from the squeeze pressure and/or cement that might work its way down the hole, a drillable bridge plug must be set approximately 20 ft below the interval to be squeezed off.

Spot and Squeeze (Block Squeeze) Without Packer

The following procedure should be adhered to when preparing to spot and squeeze without a packer:

1. RIH approximately 500 ft of 3 ½” tubing stinger on drillpipe to the bridge plug if it has been set and pull pack half a metre. If no bridge plug has been set, RUN the stinger to approximately 50 ft below the bottom perforations. Break circulation.
2. Set a balanced cement plug to at least 250 ft above the top perforations.
3. Pull back five stands above the theoretical TOC and reverse circulate clean. Do not exceed formation closure gradient (FCG).
4. Pull back one single, close the Hydril and apply maximum allowable surface pressure. The hardening time will be advised by the Cementing Contractor.
5. Spot more cement, if required. A minimum of 50 ft of cement must be left above the perforations.
6. POOH with the stinger.

Spot and Squeeze (Block Squeeze) Using a Retrievable Packer

The following procedure should be adhered to when preparing to spot and squeeze using a retrievable packer:

1. Run the retrievable packer with a tailpipe at least 100 ft longer than the length of the cement plug to be spotted with the stinger in place.
2. Set a balanced cement plug to at least 250 ft above the top perforations.
3. Pull back one stand above the theoretical TOC and reverse circulate clean. Ensure that the circulating sub is closed. Do not exceed FCG and check accurately for losses.
4. Pull back one single, set the packer and apply maximum allowable surface pressure. The hardening time will be advised by the Cementing Contractor.
5. Spot more cement, if required. A minimum of 50 ft of cement must be left above the perforations.
6. Unseat packer and POOH.

Straight Squeeze Using a Cement Retainer

The following procedure should be adhered to when preparing a straight squeeze using a cement retainer:

• Set a drillable cement retainer on drillpipe approx. 50 ft above the perforations to be squeezed off.
• Pump preflush (see Spacers).
• Displace the batch-mixed cement until the first spacer reaches the end of the stinger. Apply back pressure to the annulus to balance the cement column.
• Stab back into cement retainer immediately.
• Squeeze away the cement at a constant bottom hole pressure (BHP). The BHP used must not exceed 50 - 60 % of the formation closure pressure whilst maintaining the flow rate at easily managed levels.
• Note the flow rate and establish the trend
• If the flow rate remains constant, squeeze 50 % of the available slurry and commence a hesitation squeeze.
• Hesitate and pump for 1 to ± 10 minute steps, depending on the results.
• Pull out drill pipe from cement retainer approximately 5 ft.

Notes:

If the flow rate cannot be decreased whilst maintaining the BHP constant, PUMP a further 25 % of the available slurry.

If a flow rate decrease is noted, ALLOW the trend to continue until flow is negligible, increasing BHP by 1 000 psi increments at each step and allowing the pressure to bleed off to the previously established constant BHP value.

The final BHP must not be greater than the FCG but great enough to allow the remaining cement to be reversed out without losses.

PUMP no more than 75 % of the total available slurry

• Pull out of cement retainer approximately 5 ft and reverse clean. The returns must be measured and reported.
• POOH.

Straight Squeeze Using a Retrievable Packer

Application

Under normal circumstances, this operation must not be carried out. A drillable cement retainer must be used due to difficulties in retrieving the packer should it become stuck. Under exceptional circumstances, the technique may be used, but it must be discussed with Operations Engineer/ Drilling Supervisor beforehand.

Testing of Squeezed‑Off Perforations

The testing programme to be carried out after squeezing off perforations shall be determined by Senior Operations Engineer. Any, or all, of the following may be required:

• An inflow test may be required to evaluate the quality of the job. This is dependent on the reservoir pressure, amongst other considerations. Draw-down and time shall be clearly stipulated.
• A circulation test may be required.
• A cement evaluation log may be run before and after the job to obtain additional information.

Note: Pressure testing of the casing should not be carried out to avoid cracking of the cement bond.

Squeezing Off a Leaking Liner Lap

The procedure for squeezing off a leaking liner lap is identical to that described earlier in this section for perforations using a block squeeze with a retrievable packer.

• If a drillable bridge plug or vis-pill is to be used as a bottom for the cement, it should be set approximately 30 ft below the top of the liner.
• Straddling the liner hanger with SN-6 packer should be considered as an alternative to squeezing cement.