Domain Introduction

This topic will discuss the cementing domain and provide introductory information for the reader. This domain introduction is provided so that the reader will be familiarized with the basic concepts of cementing in order to understand and use the Cementing section of the data model. This is not an exhaustive introduction. References to more complete domain information will be provided.

The purpose of a Cement Job

There are three reasons why a cement job could be performed on a borehole:

�      To secure the casing string in place, also known as a primary cementing job.

�      To fix a hole in a casing or production liner, cement can be pumped into the hole in this casing to seal it. This type of cement job is called a squeeze cement job.

�      To plug a borehole prior to abandoning it or prior to kicking off on a sidetrack, also known as a plug cementing job.

Cement Slurry

Cement, or slurry as it is known, is mixed by two methods. It can be mixed either on the fly or batch mixed. It is then pumped from the cement unit to the drill floor.

Primary Cement Job

In a primary cement job, the cement is pumped down inside the casing where it passes into the gap (or annulus) between the casing and the open hole. The cement is then displaced from the casing by pumping down a displacement fluid (usually drill fluid).

Squeeze Cement Job

During the life of a well, it may be necessary to perform a squeeze cement job to repair corroded casing, to plug perforations to control water production, or to repair improper zonal isolation.

Plug Cement Job

Setting a cement plug in a well is a common oilfield operation. The purpose of a cement plug is to:

�      Sidetrack above a fish or to initiate directional drilling

�      Plug back a zone or plug back a well

�      Solve a lost circulation problem during the drilling phase

�      Provide an anchor for open hole tests

The most common method of placement of a cement plug is called the Balances Plug technique. In this technique, tubing or drill pipe is run in the hole to the desired depth for the plug bas. An appropriate volume of space or chemical wash is pumped ahead and behind the slurry to avoid any detrimental contamination of the cement by the mud.

Cement Job Evaluation

Once a cement job has been performed, the objectives of the cement job should be evaluated to ensure they have been accomplished. Various hydraulic and pressure tests can be run in order to validate the integrity of the casing. The most common technique to determine the quality of a cement job is a Cement Bond Log. Using this technique, sonic pulses are transmitted through the casing and into the formation behind. These pulses are then detected in a detector further down the tool, and from the time taken for each pulse to travel into the formation and back, a determination can be made as to the quality of the cement bond.

Cement Bond Log Tool

Sonic Wave Paths