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.
For most of oil based mud, lime (Ca(OH)2) is used in the system in order to perform a chemical reaction with fatty acid emulsifiers. Typically, 3 to 5 lb/bbl of lime is added in the drilling mud so that there is enough hydroxide (OH-1) ions to keep the emulsion stability in good shape.
Moreover, lime (Ca(OH)2) will control acid gases such as H2S and CO2. The following chemical equations demonstrate how lime reacts with H2S and CO2, respectively.
Ca(OH)2 + H2S -> CaS + 2(H2O)
Ca(OH)2 + CO2 -> CaCO3 + H2O
If drilling into zones where CO2 or H2S exists, the amount of excess lime should be increased to around 5 to 10 lb./bbl., because some lime is used for emulsion stability and others react with acid gases to maintain the mud’s properties.
What’s more, when the well is drilled into formations containing H2S, the excess lime must be kept constantly at 5 to 10 lb/bbl all the time. Do not try to reduce the amount of excess lime because the chemical reaction between H2S and lime is reversible. Therefore, if the level of excess lime is not maintained, the H2S gas can be released at the surface from the reversible chemical process.
Andy Philips, 2012. So You Want to be a Mud Engineer: An Introduction to Drilling Fluids Technology. Edition. CreateSpace Independent Publishing Platform.
Ryen Caenn, 2011. Composition and Properties of Drilling and Completion Fluids, Sixth Edition. 6 Edition. Gulf Professional Publishing.
The Electrical Stability (ES) is one of the vital properties for oil based mud. It shows the voltage of the current flowing in the mud. The ES number represents the mud emulsion stability. The more ES is; the more the emulsion stability is.
Oil based fluid is a non-conductive material. Therefore, the base fluid will not transfer any current. Only the water phase in the mud will conduct the electricity. If the mud has good emulsion, you will have high ES figures. On the other hand, if the emulsion of the mud is bad, you will have low ES value.
The Electrical Stability (ES) is obtained from an electrical stability tester kit (see the image below).
Electrical Stability Meter
Saudi Arabia has the second largest oil reserves in the world, so it is quite logical that there are several successful oil companies in this country. One of them is Saudi Aramco or simply Aramco. With a revenue of around $380 billion and value between $2 trillion and $10 trillion, Saudi Aramco is the most valuable company in the world.
One of the reasons why this company is always on top is their investment in research and development of new oilfields. Manifa oilfield is one of these new oilfields that have proven to be a great investment.
Manifa oilfield is located on a manmade island. Thanks to modern technology, engineers and architects can create artificial islands and make the production of oil much easier and simpler. Of course, in order for such manmade island to promise a good return on investment, it must be situated in shallow waters. Otherwise, it will need a lot of material to build it. At the same time, these manmade islands guarantee the improvement of long-term reservoir recovery. In addition, oilfields built on manmade islands allow the creation of more wells, don’t have negative environmental effects and it is much safer for the workers to work on an oilfield like this.
Manifa Field (Top View)
With regards to the major catastrophic incident, BP Deep Water Macondo which happened on 20 April 2010, many companies in the oil and gas industry tend to heavily invest in extra Health, Safety and Environment (HSE) programs in order to raise the HSE awareness and standard for their employees. These non-compulsory HSE plans have been introduced into a company in different ways such as in-house initiatives and third party HSE training services. For many years, the price of oil was slightly above 100 $/bbl and the spending extra budget on safety programs was an acceptable practice across the industry. Therefore, the budget at HSE has increased dramatically over this period of time.
However, since mid-2014, the oil price has drastically dropped from about 110$/bbl to 50$/bbl as of October 2016. Most companies in the upstream business have had extremely bad effects on their incomes; they therefore have looked into ways to reduce operating expenditures without compensating their reputation, safety, reliability, and product quality and harming their people. One aspect to help corporations achieve this goal is to optimize the HSE practices.