In order to properly design a completion, reservoir rock and fluid properties must be carefully taken into account because they directly influence on equipment selection. Reservoir properties (rock and fluid properties) which must be considered are as follows;
Low permeability formation may require fracturing operation to enhance production. The completion for tight formations must be able to withstand pumping pressure and allow fracking fluid and proppant to flow through.
Unconsolidated formations are required to complete a well with a sand control completion; thus, a well can be produced without any damage to downhole and surface equipment.
Reservoir pressure directly affects the pressure rating on all completions because all components must be able to work under reservoir condition. What’s more, formation pressure will affect how much flow of the well can produce.
High reservoir temperature will quickly degrade some components, especially elastomer, and this will result in well integrity issues due to pressure leakage. This is one of the critical concerns in selecting the right equipment to work under high temperature conditions. Continue reading
Mechanical properties of material are one of the most important basic concepts in a well design and this section will briefly discuss about key mechanical properties and their applications. Furthermore, there is a discussion about effect of corrosion on the mechanical performance of load carrying components.
Mechanical Properties of Material
Basic mechanical properties are as follows;
Hardness is a resistance of materials to permanent deformation and is sometimes referred to a resistance to abrasion or scratching. The greater of the hardness, the harder it is for the materials to deform. The application of hardness is to inspect if materials have been properly treated during a heat treatment process. The comparison between the actual hardness and the standard hardness of materials will show whether the current batch of material is proper and suitable for use or not.
Strength of material is an ability to work within a load without failure of the material. Tensile and yield strength are critical properties in terms of material strength.
Tensile strength or ultimate tensile strength is the maximum stress on an engineering stress-strain curve. At this point, materials are plastically deformed but they may not be broken apart yet depending on types of materials. Continue reading
The Organization of the Petroleum Exporting Countries (OPEC) has agreed to cut supply by 1.2 million barrels per day (bpd) to 32.5 million barrels, the head of the organization announced.
Ahead of the official announcement, Bloomberg broke the news, quoting an unnamed delegate in Vienna. Crude prices soared more than 7 percent on the report. As of 16:29 GMT, Brent crude was trading at nearly $50 per barrel, while US crude benchmark WTI was above $48.
Calling the decision “historic,” the organization said the output cut would be in effect from January 1, 2017. The deal was reached after weeks of negotiations, as Saudi Arabia, Iraq and Iran fought for the very last barrel of production. This is the first coordinated cut from OPEC in eight years. Continue reading
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.