Casing and tubing strings are the main parts of the well construction. All wells drilled for the purpose of oil or gas production (or injecting materials into underground formations) must be cased with material with sufficient strength and functionality. Casing is the major structural component of a well. The cost of casing is a major part of the overall well cost, so selection of casing size, grade, connectors, and setting depth is a primary engineering and economic consideration. Conductor casing is the first string set below the structural casing (i.e., drive pipe or marine conductor run to protect loose near-surface formations and to enable circulation of drilling fluid).
New pages are continually added to PetroWiki. These new pages always need subject experts to help develop these pages into high quality resources. With so many different roles within PetroWiki that have to do with contributing there is undoubtedly a place that will fit perfectly with your expertise and time. A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks. Hydrotesting of pipes and/or pipelines are performed to expose defective materials that have missed previous detection, ensure that any remaining defects are insignificant enough to allow operation at design pressures, expose possible leaks and serve as a final validation of the integrity of the constructed system.
Environmental hazards can be reduced or prevented by the proper choice of chemical additives at optimum concentrations. Pressure tests are performed with water or brine to ensure the absence of leaks in pressure piping, tubing, and packer. Leaks on the surface can endanger service personnel, and subsurface leaks can cause subsequent corrosion of tubing and casing in the annulus. Those handling chemicals and valves should wear protective gauntlet-type, acid-resistant gloves. Fresh water and spray washing equipment should be available at the job site.
Most threats to safety from production involve the release of hydrocarbons; therefore, the analysis and design of a production-facility safety system should focus on preventing such releases, stopping the flow of hydrocarbons to a leak if it occurs, and minimizing the effects of hydrocarbons should they be released. Ideally, hydrocarbon releases should never occur. Every process component is protected with two levels of protection: primary and secondary. The reason for two levels of protection is that if the first level fails to function properly, a secondary level of protection is available. If hydrocarbon releases occur (and, in spite of our best efforts, they sometimes do), inflow to the release site must be shut off as soon as possible.
Production facilities usually operate according to design. Oil and gas travel from the reservoir to the surface facilities where they are separated, cleaned, measured, and sent through a pipeline to the end user. During most of this process, everything operates according to plan. Such problems usually can be solved quickly and easily without negative consequences. Unfortunately, some problems have the potential for serious consequences such as injury to personnel, pollution of the environment, and loss of company assets.
A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks. Hydrotesting of pipes and/or pipelines are performed to expose defective materials that have missed previous detection, ensure that any remaining defects are insignificant enough to allow operation at design pressures, expose possible leaks and serve as a final validation of the integrity of the constructed system. Buried high pressure oil and gas pipelines are tested for strength by pressurizing them to at least 125% of their maximum operating pressure (MAOP) at any point along their length. Since many long distance transmission pipelines are designed to have a steel hoop stress of 80% of specified minimum yield (SMYS) at MAOP, this means that the steel is stressed to SMYS and above during the testing, and test sections must be selected to ensure that excessive plastic deformation does not occur. Leak testing is performed by matching changes in the measured pressure in the test section against the theoretical pressure changes calculated from changes in the measured temperature of the test section.
Liquid loss from a storage tank is generally caused by localized material failure in the form of localized corrosion. Tank bottom leaks can be a result of improper foundation design or operating a tank outside the recommended design pressure or temperature boundaries. Product liquid leakage remains a significant environmental concern. Any tank used to contain a hydrocarbon product can be prone to develop leaks sometime during the service life. Tank design options that reduce the risk of a leak can be considered, or in the event of a leak, any product that escapes is contained and detected in a realistic time frame.
Siddiqui, Muhammad Ali (OMV Pakistan Subsidiary of United Energy Group – UEG) | Hassan, Syed Saadat (OMV Pakistan Subsidiary of United Energy Group – UEG) | Mubasher, Muhammad (OMV Pakistan Subsidiary of United Energy Group – UEG) | Latif, Saqib (OMV Petrom) | Dar, Usman Anjum (Schlumberger)
The objective of writing this success story is to demonstrate how technology, in particular low cost solutions, are key to economically sustain and secure production from mature fields. Tubing Patch technology has been successfully utilized in Pakistan for the first time to restore the well integrity and saved huge CAPEX by avoiding expensive rig workover.
Tubing-Annulus pressure suddenly increased in one of water disposal well (WDW). Annulus pressure varied directly with variations in Injection rates which were the clear evidence that tubing-annulus communication had been established and basic check ascertains that well had integrity issue. Being the only injector in area all production and processing of gas is majorly dependent on its injection reliability and integrity. After detailed in-house working it was decided to run diagnostic logging with spinner (quantitative) & temperature log (qualitative) to identify the leakage points precisely. All potential leakage paths (packer, tubing, tool joints) were considered while selecting the diagnostic techniques to have conclusive results. Based on diagnostic logging three leakage points were identified. Before proceeding for remedial measures to restore the well integrity, it was mandatory to check health of old carbon steel tubing string therefore it was planned to acquire corrosion log. Based on corrosion logging results, completion tubular was established in good condition which steered to install tubing patches best Techno-Economical solution across the leaks to restore well integrity instead of rig workover for re-completion.
Consequently, three tubing patches, were successfully applied using wireline in water disposal well and integrity of well was restored. C-Annulus was pressure tested even after six months of installation and no pressure drop was observed during this interval.
Downhole casing repair is a major workover operation worldwide, especially in wells which were drilled and put on production decades ago. The presence of corrosive formations is considered a common downhole source that slowly corrodes steel strings over time. Several remedial options are available on the commercial shelf including cement slurry, resin chemicals, and mechanical casing patch technologies. Yet, these suffer from several disadvantages including limited isolation and integrity, cost, internal diameter restriction, etc. These drawbacks could lead to casing leaks reoccurring across the same depth shortly after applying the commercial treatments. In other scenarios, they result in internal diameter reduction and inability to pass tools, such as plugs, packers, whipstocks, etc. The proposed epoxy resin formulation retains improved mechanical and chemical properties over the commercial products to repair challenging downhole casing leaks, especially those with low injectivity.
This formulation is composed of a combination of two different resins and one curing agent. Compared to other commercial epoxy and polyester products, this formulation showed lower rheology of less 50% at room temperature, deeper crack penetration, improved compressive strength and elasticity, and enhanced corrosion resistance.
The product was deployed in the field to cure downhole 7 in. casing leaks with 73 pcf CaCl2 brine in place. The subject leak showed low injectivity of 0.4 bpm at 1,000 psi, requiring solid-free solutions. The innovative formulation was introduced as a result, and 20 bbl were spotted as a balanced plug and squeezed in hesitation to achieve the required pressure integrity of 600 psi after resin plug cleanout. Manganese Tetroxide was used as the weighing agent to mix up 80 pcf epoxy resin as per design. The low-rheology allowed for maximum injected volume at the required lock-up pressure of 1,000 psi. Meanwhile, the elastic nature enabled more resistance during the following re-entry operations and relatively higher rates of penetration during resin plug cleanout.
This paper will discuss the nature of the resin formulation and experimental work to compare this innovative product to the commercial products. The pilot testing, job simulation, and field deployment will be highlighted to emphasize the added value and potential of this product.