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The most important mechanical properties of casing and tubing are burst strength, collapse resistance and tensile strength. These properties are necessary to determine the strength of the pipe and to design a casing string. If casing is subjected to internal pressure higher than external, it is said that casing is exposed to burst pressure loading. Burst pressure loading conditions occur during well control operations, casing pressure integrity tests, pumping operations, and production operations. The MIYP of the pipe body is determined by the internal yield pressure formula found in API Bull. This equation, commonly known as the Barlow equation, calculates the internal pressure at which the tangential (or hoop) stress at the inner wall of the pipe reaches the yield strength (YS) of the material.
Abstract To successfully carry out a workover on a well that was completed more than 20 years ago as a dual string completion with a dual packer and two Permanent Packers is complicated. The presence of a slickline fish of unknown dimensions in hole further complicated the nature of the workover thus making it susceptible to failure during the retrieval of the tubings. A Tubing Integrity Evaluation Methodology (TIEM) was used to properly assess potential failure points and craft out execution strategy to mitigate them. The TIEM adopted in this paper involved carrying out a detailed tubing stress analysis on the completion tubings where axial loads exerted on the tubing; weight, buoyancy, point loads on crossovers, piston loads, ballooning; as well as triaxial stress effect of axial, radial and tangential stresses were all estimated. The yield strength and yield stress completion tubing were de-rated by 30 percent as a precautionary measure due to the age of the completion tubings. The maximum overpulls the tubings could sustain without failing by parting, axially or yielding triaxially were calculated. These overpull forces was compared with the force required to unseat the dual packer as well as snap out from seal assemblies of the permanent packers to decide whether the tubing was to be cut prior to pulling or not during the tubing retrieval operation. Several fishing scenarios of slickline and drill pipe fishing were analysed based on the location of the slickline fish. Based on the results of the detailed tubing stress analysis, the maximum overpull the short string and long string sections could sustain were 58,000 lbs and 23,000 lbs respectively while the maximum force required to unseat the dual packer was 50,000 lbs. Thus, it was decided to pull the short string within the overpull limit while the long string was to be cut above the packer prior to unseating the packer. The Tubing evaluation helped to properly assess potential failure points and craft out execution strategy to mitigate or avoid potential problems associated with the workover operations with unknown dimensions of fish in the wellbore.
Abstract The use of a post-yield design basis for thermal service tubulars (such as in cyclic steam stimulation, continuous steam injection, and geothermal wells) is common in the industry. However, very few case studies have appeared in the literature on the application of these methods and the quantitative impact of their use on the well design. In this paper, we present the use of a post-yield design approach to design thermal service wells that is based on work presented by Suryanarayana and Krishnamurthy (2015). The design approach was applied in two recent thermal service well designs. Working Stress Design is used to confirm the suitability of the tubular for life cycle loads except for those load cases that are dominated by stresses arising from temperature change (i.e., thermal loads). For thermal loads, post-yield design approaches based on Modified Holliday and Low Cycle Fatigue (LCF) are used. The work flow is presented and discussed in terms of practical application of the approach. Two different case studies are presented - a cyclic steam stimulation case, and a geothermal well case. The method is applied to all the tubulars in the well, but this paper will focus on the production casing. Threaded connections are treated as strain localization points, and are included in the LCF design approach. Practical design issues such as impact of cement shortfall, directional control, and parameter uncertainties are discussed. The design implications of applying a post-yield design basis are shown to be significant in some cases. The design optimization and alternative design choices that resulted from the application of this approach are discussed. Finally, ongoing work to enhance the design approach is discussed. The authors believe this work provides a practical basis for design of thermal service wells.
Abstract At the beginning to handle sand production is using mechanical methods (gravel pack, slotted liner, sand screen, and others). This method is successful to hold the sand on consolidated formation in the reservoir, but not success for formation with a poorly consolidated and unconsolidated formation. The purpose of this research is to produce hydrocarbons (gas) without producing sand. The method is making a strength bonds between sand particles (sand consolidation) using chemicals (resin) without reduce to much the value of porosity and permeability. This research is using artificial core which made based on unconsolidated formation of reservoir characteristics, such as: (i) matrix grain size in the range of mesh size between 80-120, (ii) Cemented between the matrix is weak, (iii) 25-30% Porosity, (iv) 50-300 mD permeability. Experiment condition conducted at reservoir temperature and pressure, which is 102 ° C and 3145 psi. Testing of resin effect to the strength of rock stress is done by triaxial stress, which developed and manufactured with the application of high pressure, high temperature, the axial pressure, and radial pressure that using gas and liquid fluid. The results of this study show that mixing a resin with core can increase rock strength up to 700-800 psi, which can handle sand problems.
Temperature Why Are Details More Important?
Transport properties are important parameters in controlling reservoir performance, and an understanding of how fluids flow through a reservoir can aid successful management of hydrocarbon recovery. Traditional laboratory measurements of permeability and resistivity are carried out in one direction which does not take into account any anisotropy in the rock properties. Furthermore, laboratory measurements of these properties are often carried out under conditions of equivalent hydrostatic stress, or sometimes anisotropic triaxial loading in which two of the principal stresses are equal. However, permeability and resistivity may vary in the three principal directions, and pore volume change may differ under different stress paths. A novel method for measuring directional permeability and resistivity on a cubic sample under realistic true triaxial stresses has been developed and used in this study. This paper presents laboratory measurements of directional permeability, directional resistivity and pore volume change under conditions of hydrostatic and true triaxial stresses. Measurements of permeability and resistivity were carried out in the three principal directions using cubic rock samples of outcrop and reservoir sandstones. The main objectives of the work was to investigate directional and stress dependence of transport properties under realistic true triaxial stresses. Results have shown greater pore volume change to occur under comparable hydrostatic compared to true triaxial stresses. The samples with laminations showed high degrees 1Currently with Petroleum Development Oman (PDO)of anisotropy in permeability and resistivity under conditions of hydrostatic and true triaxial stresses. The degree of anisotropy was found to be constant between low and high stress. The permeability values were found to be higher under true triaxial stresses than under their corresponding equivalent hydrostatic stresses, whilst resistivity showed little differences. Thus the results have shown the importance of measuring directional transport properties and pore volume changes under realistic stress conditions.
This paper was prepared for presentation at the SPE Applied Technology Workshop on Risk Based Design of Well Casing and Tubing held in The Woodlands, Texas, U.S.A., 7–8 May 1998.