A number of components are fitted to the casing string to enable it to be cemented in place. In order to successfully cement each casing string, casing accessories should be installed and the necessary components are listed below;
A float shoe is a short and rounded shape component with non-return value inside which is installed at the end of the casing. The advantages of a float shoe are as follows;
Prevent mud flowing back while running casing and prevent cement from outside U-tubing back into casing due to unbalanced conditions while performing cementing operation.
Help running casing to the well. The round shape of a float shoe prevents a casing string from hanging up and guiding a string into a wellbore. Some float shoes are made of high strength drillable material and can be used to reciprocate and rotate to pass any obstructions in a wellbore.
Cementing is very critical step of well construction. Bad cement job can lead to bad situations as well control, low productivity, gas channeling in annulus, etc. Therefore personnel in oilfield should learn and understand this topic. It is quite hard to find very good vdo training in the topic of oil well cementing but we finally find it. This VDO training is very excellent because it teaches all the basic with animations which absolutely helps learners fully understand this topic. Additionally, we add full VDO transcript so it will help some people who cannot catch all the wording in the VDO training. Please feel free to add comments and/or suggestions and we wish you would enjoy learning from this post.
Full VDO Transcript
Here is an overview of casing cemented in a well called primary cementing. The cement’s main jobs are to completely isolate or totally seal off all the oil, gas and water zones from the well bore and to bond the casing firmly to the wall of the whole. Here the crew has drilled the well to the casing point, the depth at which they will set and cement casing. The driller circulates drilling mud to clean the hole and to make sure the mud is in good condition. Then the crew pulls the drill string out of the hole. The next step in primary cementing is for the casing crew to run the casing into the well, one joint at the time. Notice at the bottom of the casing, the guide shoe and float collar. Also notice the centralizers and scratchers. The guide shoe guides the first joint of casing into the well bore. A valve in the float color lets the crew float the casing into the well to lessen the load on the rig’s hoisting system. Continue reading →
One function of cement is to support casing string and the shear strength of cement holds casing string once cement is set. You may think about other load supporting casing as compressive loading at coupling areas or thermal movement. They are the part of the supporting force as well but the most support is from the cement shear strength.
(Diagram above shows how shear strength of cement supports casing string)
We don’t normally measure shear strength of cement but we can apply knowledge from Civil engineer to estimate the shear strength from the compressive strength. Generally, cement has the shear strength approximately 1/12 of compressive strength. For instant, if the cement 1000 psi compressive strength, its shear strength is 83.3 (1000 x 1/12) psi.