Primary Cementing
The initial cement job used to support and seal casing in a wellbore. This operation is critical for establishing well integrity by bonding the casing to the surrounding formation and preventing fluid migration between subsurface zones.
Remedial Cementing
Cementing performed after the primary job to correct issues such as fluid leaks, channeling, or poor zonal isolation. It includes operations like plug placement or squeeze jobs to restore well integrity.
Squeeze Cementing
A pressure-pumping technique in which cement is forced into specific problem zones to seal off leaks or voids in the casing or formation. It is commonly used to shut off water or gas production from unwanted zones.
Zonal Isolation
The strategic sealing of specific underground zones to prevent communication between different formation layers. Achieving effective zonal isolation is essential for safe, efficient production and regulatory compliance.
Casing
Steel pipe installed in a wellbore to stabilize the well, support the sides, and isolate different pressure zones. The casing is cemented in place to ensure a secure and durable well structure.
Centralizer
A mechanical device fitted around the casing to keep it centered in the wellbore. Proper centralization ensures uniform cement distribution, which is vital for effective bonding and zonal isolation.
Float Collar / Float Shoe
Components located at the bottom of the casing string. The float collar acts as a landing point for cementing plugs, while the float shoe assists in guiding the casing and provides a one-way valve to prevent backflow of fluids.
Top Plug / Bottom Plug
Cementing plugs used to separate fluids during a cementing job. The bottom plug clears the casing of mud before cement enters, and the top plug separates the cement from displacement fluids, ensuring accurate placement.
Displacement Fluid
The fluid used to push cement through the casing and into the annulus between the casing and borehole wall. It must be carefully selected to prevent mixing with the cement and to ensure proper displacement efficiency.
Surface / Intermediate / Production Strings
Different casing strings installed at various depths during well construction. Each string serves a unique purpose and must be cemented to secure the well structure and isolate formation zones.
Cement Slurry
A fluid mixture of cement, water, and various additives that is pumped into the wellbore and allowed to set. Once hardened, it forms a seal around the casing to support the well and provide zonal isolation.
Additives
Specialized materials added to cement slurries to alter properties such as density, viscosity, set time, and strength. Common additives include retarders, accelerators, extenders, and fluid loss agents.
Retarder
A chemical additive that slows down the setting time of cement. Retarders are essential in high-temperature or deep wells where cement might otherwise set too quickly before proper placement is achieved.
Accelerator
An additive that speeds up the setting time of cement, particularly useful in low-temperature or shallow wells where faster setting can reduce wait times and improve operational efficiency.
Lost Circulation
A condition where drilling fluid or cement is unintentionally lost to underground formations with high permeability or fractures. It can complicate cementing operations and requires specialized techniques to mitigate.
API Standards
Specifications and practices published by the American Petroleum Institute (API) to ensure quality, safety, and consistency in oilfield operations, including cement formulation, equipment, and procedures.
Bond Log
A type of well log that evaluates the quality of the cement bond between the casing and the surrounding formation. Bond logs help assess the effectiveness of zonal isolation and cement integrity.
Annulus
The space between the casing and the wellbore wall. This area is filled with cement during a cementing job to provide structural support and isolate formation zones.
Wait-on-Cement (WOC)
The mandatory period after cement placement during which operations pause to allow the cement to set and develop sufficient compressive strength. WOC time is critical for well safety and integrity.
Pressure Testing
A quality control step after cementing where pressure is applied to the casing to confirm the integrity of the cement job and identify any leaks or weak spots before proceeding with further well operations.
