The article introduces a method to calculate the depth for surface casing and inter-mediate casing setting in wells where gas, oil and water shows might occur. The described method refines and specifies the requirements of current regulations. The surface casing shoe depth must cover unstable rock formations prone to fluidity, prevent rock fractures during cement hydrotesting after drilling the casing shoe. It also enables to avoid rock fractures in open hole below the shoe due to internal pressure when replacing drilling fluid with reservoir fluids or mixed fluids from different layers. These rules are written as systems of equations and inequalities, covering cases where the well is filled with oil, gas and gas-liquid mixtures. Manual depth calculation is possible using these formulas, but it involves complex steps and sequential condition checks. To simplify this, a computer program was developed to automate the process of calculation. An example of a field in Western Siberia illustrates the method. It includes the surface casing depth calculation as well as pressure for testing the surface casing and its cement seal calculation. This approach is suitable for designing oil and gas wellbore construction. It enhances reliability and safety in challenging drilling conditions, offering a practical tool for engineers.
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URL: http://docs.cntd.ru/document/499011004
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