Introduction to Well Cementing

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Cementing Regulations

Before a well can be drilled, the operator must obtain a drilling permit from the appropriate regulator. Every country or state within a country, from Uganda to Wyoming, has a regulatory agency (Uganda Ministry of Energy and Mineral Development; the Wyoming Oil and Gas Conservation Commission, for example) that issues regulations that govern the design, permitting, drilling, and abandonment of oil and gas wells within their jurisdiction. In some cases a second agency exists that is charged with the protection of the surface and subsurface environment (for example, the US Environmental Protection Agency). The regulations cover all aspects of the well to be drilled and, with respect to cementing, they typically include:

Casing and cementing depth
Cement type
Cement circulation
Permit and reporting requirements

In addition to providing guidance or specific requirements for cementing all the tubulars in the hole, many regulatory agencies also have formal reporting portals on websites that are used to report progress during cementing and for filing of final reports after the job is done. Often a representative of the regulatory agency will visit the well site during cementing, review logs and reports, the well plan submitted for the drilling permit, and generally ensure that the cementing operation is following the regulations.

An Example

For example, here are the requirements for preparing and submitting a Casing and Cementing Plan to the Commonwealth of Pennsylvania, Department of Environmental Protection:

Casing and Cementing Plan (Title 25, Environmental Protection, Subchapter D, Well Drilling, Operations, and Plugging, Chapter 78 Oil and Gas Wells, Section 83a)

The operator shall prepare and maintain a casing and cementing plan showing how the well will be drilled and completed. The plan must demonstrate compliance with this subchapter and include the following information:
1. The anticipated depth and thickness of any producing formation, expected pressures, anticipated fresh groundwater zones and the method or information by which the depth of the deepest fresh groundwater was determined.
2. The diameter of the borehole.
3. Casing type, whether the casing is new or used, depth, diameter, wall thickness and burst pressure rating.
4. Cement type, yield, additives and estimated amount.
5. The estimated location of centralizers.
6. The proposed borehole conditioning procedures.
7. Alternative methods or materials as required by the Department as a condition of the well permit.
Upon request, the operator shall provide a copy of the well-specific casing and cementing plan to the Department for review and approval.
Revisions to the plan made as a result of onsite modification shall be documented in the plan and be available for review by the Department. The person making the revisions to the plan shall initial and date the revisions.

DEP Regulations for WOC

After cementing operations are complete, the casing cannot be disturbed for a minimum of 8 hours. The following operations cannot be conducted:

Within 4 hours: Releasing pressure on the cement head if float equipment did not hold. After 4 hours, the pressure may be released at a continuous, gradual rate over the next 4 hours, provided the floats are then secure.
Within 8 hours: Nippling up on to the casing.
Within 8 hours: Slacking off by the rig supporting the casing in the cement sheath.
Within 8 hours: Running drill pipe, or other mechanical devices into or out of the wellbore. The only exception is wireline used to determine the top of cement.

A copy of the cement job log must be available at the well site for inspection by the DEP. The job log must include the following:

Mix water temperature $°F$
Mix water pH
Type of cement
Type and quantity of additives
Volume of cement $bbl$
Yield of cement $\tfrac{ft^3}{sk}$
Density of cement $ppg$
Volume of cement returns to surface [bbl]
Pumping rates $\tfrac{bbl}{min}$
Final Circulating Pressure $psi$
Total Pumping Time $min$
Sequence of events during the cementing operation

The same agency has reporting requirements for oil and gas wells. With respect to cementing they include:

Well Reporting (Title 25, Environmental Protection, Subchapter E, Well Reporting)
Electronic Notifications: The notifications listed below are to be submitted via the DEP electronic reporting website:
- Spud Notice – 24 hr. notice prior to the commencement of drilling (setting conductor). Only the conductor rig should be providing this notice.
- Break in drilling of 30 days or more – 24 hr. notice.
- Casing cementing notification – 24 hr. notice prior to cementing all casing strings.
- Production casing pressure test – 24 hr. notice
- Stimulation – 24 hr. notice.
- Plugging – 24 hr. notice.
Additional Notification Requirements: The notifications listed below are to be made by email and/or phone call to the appropriate Oil and Gas Inspector.
- o Surface Casing Cement not circulated to surface – If cement used to permanently cement the surface or coal protective casing is not circulated to the surface despite pumping a volume of cement equal to or greater than 120% of the calculated annular space, we are to determine the top of cement and notify the Department (Oil and Gas Inspector).
- o For each well that is drilled or altered, the operator shall keep a detailed drillers log at the well site available for inspection until drilling is completed. Within 30 calendar days of cessation of drilling or altering a well, the well operator shall submit a well record to the Department on a form provided by the Department.

The regulations with respect to drilling and cementing of casing are extensive and must inform the drilling and completion plan. The plan, in turn, must be carefully followed during application or operators can risk major fines.

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