Evaluation of Corrosion, Mechanical Properties and Hydrogen Embrittlement of Casing Pipe Steels with Different Microstructure

In the research, the corrosion and mechanical properties, as well as susceptibility to hydrogen embrittlement, of two casing pipe steels were investigated in order to assess their serviceability in corrosive and hydrogenating environments under operation in oil and gas wells. Two carbon steels with different microstructures were tested: the medium carbon steel (MCS) with bainitic microstructure and the medium-high carbon steel (MHCS) with ferrite–pearlite microstructure. The results showed that the corrosion resistance of the MHCS in CO2-containing acid chloride solution, simulating formation water, was significantly lower than that of the MCS, which was associated with microstructure features. The higher strength MCS with the dispersed microstructure was less susceptible to hydrogen embrittlement under preliminary electrolytic hydrogenation than the lower strength MHCS with the coarse-grained microstructure. To estimate the embrittlement of steels, the method of the FEM load simulation of the specimens with cracks was used. The constitutive relations of the true stress–strain of the tested steels were defined. The stress and strain dependences in the crack tip were calculated. It was found that the MHCS was characterized by the lower plasticity on the stage of the neck formation of the specimen and the lower fracture toughness than the other one. The obtained results demonstrating the limitations of the usage of casing pipes made of the MHCS with the coarse-grained ferrite/pearlite microstructure in corrosive and hydrogenating environments were discussed.

Gas Well Deliquification in the Presence of High Content of Condensate: From Laboratory to Field Test

Two foaming formulations, an amphoteric surfactant (noted as Fam) and a blend of anionic-cationic-amphoteric surfactants (noted as Facam) have been prepared and tested at lab and in field in the presence of high content of condensate (60 vol% on average). Foam height with Facam are close to those with Fam. Although Fam has better foam stability without condensate, the half-life of the foam (t1/2) decreases by 50% in presence of condensate. Foam generated by Facam shows better oil resistance performance due to negative spreading coefficient (S). Liquid unloading efficiency with Facam are close to those with Fam at lab. Nevertheless in field application, Facam is more efficient than Fam for the deliquification in the gas well. The depth of gas well is 2126 m. Foaming formulations were injected respectively from casing pipe with injection amount of 1-2kg/day. The pressure difference between casing and tubing pipes (ΔPc-t) decreased from 1.0 MPa to 0.28 MPa, and the decline of gas production was slowed down after the injection of Facam in the gas well. As a contrast, both theΔPc-t and decline rate of gas production were increased with Fam. Foam resistance to condensate is a factor, while emulsion viscosity is inferred to be another crucial factor for the performance of formulations in the deliquification process.

STUDI FONDASI TIANG BOR UNTUK JEMBATAN DI LAUT

Structurally, the bridge is separated into the upperstructure, and substructure such as foundation. According to its function, the foundation of the bridge supports and transmits the load from the superstructure to a strong and stable layer of soil. The construction of a bridge at sea has a high level of difficulty and risk. There are forces that influence the foundation at sea. The greater the loads that are held by the foundation, the greater the bearing capacity required for the foundation. The foundation used the bored pile casing method. The concept of a bored pile foundation casing method itself uses a steel casing pipe that is installed to a specified depth. This method is used when the borehole is very prone to landslides, so it is very suitable to be applied to soil which is sand below the groundwater level or at sea. In this paper, we will discuss the bearing capacity of the bored pile foundation and the loads that affect the bearing capacity of the foundation. Bearing capacity includes axial and lateral bearing capacity. So the results of this study will show how much effective bearing capacity must be considered when creating a foundation for bridges at sea.Secara struktural jembatan dipisahkan menjadi struktur atas, dan struktur bagian bawah seperti fondasi. Sesuai fungsinya, fondasi jembatan menopang dan meneruskan beban dari bangunan atas jembatan ke lapisan tanah yang kuat dan stabil/solid. Pembangunan jembatan panjang di tengah laut memiliki tingkat kesulitan dan resiko tinggi. Terdapat gaya-gaya yang mempengaruhi fondasi yang dibuat di laut. Semakin besar beban-beban yang ditahan fondasi maka semakin besar pula daya dukung yang dibutuhkan fondasi. Fondasi yang dipakai adalah fondasi tiang bor dengan metode casing. Konsep dari fondasi tiang bor metode casing sendiri menggunakan pipa selubung baja (casing) yang diinstall sampai kedalaman yang ditentukan. Metode ini digunakan bila lubang bor sangat mudah longsor, sehingga sangat cocok untuk diaplikasikan pada tanah yang merupakan pasir di bawah muka air tanah atau di laut. Pada penulisan ini akan dibahas mengenai daya dukung fondasi tiang bor dan beban-beban yang mempengaruhi daya dukung fondasi tersebut. Daya dukung mencakup daya dukung aksial dan lateral. Sehingga hasil studi ini akan menunjukan seberapa besar daya dukung efektif yang harus dipertimbangkan pada saat ingin membuat fondasi untuk jembatan di laut.

DRILLING BOREHOLES WITH SIMULTANEOUS CASING

The conditions for applying the method of drilling boreholes with simultaneous casing are considered. The most used tool designs, their advantages and disadvantages are shown. Present-day requirements for this tool are indicated. A new design is presented, which allows further drilling through the casing pipe of maximum possible diameter, simulation results are given. The operation of the device is described and a diagram of its use is presented.

Zjawiska chemiczno-technologiczne podczas zabiegu cementowania otworu w aspekcie projektowania rur okładzinowych ze szczególnym uwzględnieniem ich wytrzymałości na zgniatanie i rozrywanie

One of the most important issues that needs to be addressed in the borehole design process is the optimal design of the borehole structure, including the appropriate selection of individual casing columns and their setting given the assumed geological and cementing-technical conditions. Specific geological and technical conditions imply a number of both conditions and constraints. A kind of dimensional unification of pipes adopted by API many decades ago, i.e. a series according to the outer diameter of the pipes, constitutes the main natural constraint. Other elements of this unification, such as a series of steel grades or of classic and PREMIUM thread connections were implemented gradually as drilling technology developed. Regardless of these conditions, one thing always remains the same when designing casing and selecting production tubing, i.e. maintaining the balance between the existing loads acting on the pipes during the drilling process and operation of the borehole and the minimum mechanical strength of the pipes. This article reviews the methods and guidelines for casing pipe designing published by API and of computer programs, including StressCheck, which is currently one of the commonly used pipe design tools. The strength issues discussed in the article refer mainly to the pipe body, ignoring the complex issue of the strength of the thread connections, especially those of PREMIUM type, whose qualification is not subject to API standards, but to the guidelines contained in ISO 13679.

Technological aspects of cased wells construction with cyclical-flow transportation of rock

A high-performance technology for constructing cased wells is proposed. Essence of the technology is the advance insertion of the casing pipe into the sedimentary rock mass and the cyclical-flow transportation of the soil rock portions using the compressed air pressure supplied to the open bottomhole end of the pipe through a separate line. Results of mathematical modeling for the process of impact insertion of a hollow pipe into a soil mass in horizontal and vertical settings are considered. Modeling of the technology is implemented by the finite element method in the ANSYS Mechanical software. Parameters of the pipe insertion in the sedimentary rock mass are determined - value of the cleaning step and the impact energy required to insert the pipe at a given depth. Calculations were performed for pipes with a diameter from 325 to 730 mm. Insertion coefficient is introduced, which characterizes the resistance of rocks to destruction during the dynamic penetration of the casing pipe in one impact blow of the pneumatic hammer. An overview of the prospects for the application of the proposed technology in geological exploration, when conducting horizontal wells of a small cross-section using a trenchless method of construction and borehole methods of mining, is presented. A variant of using the technology for determining the strength properties of rocks is proposed. Some features of the technology application at industrial facilities of the construction and mining industry are considered: for trenchless laying of underground utilities and for installing starting conductors when constructing degassing wells from the surface in coal deposits. Results of a technical and economic assessment of the proposed technology efficiency when installing starting conductors in sedimentary rocks at mining allotments of coal mines are presented.

Experimental measurement of dynamic loading and numerical analysis of gas pipeline damaged by corrosion

The paper presents the results of the expert works in the area of diagnostics, repair, and reconstruction of the steel pipelines of the transit gas pipeline (TP) on Slovak territory. One part of our work included dynamic measurements of a steel casing pipe located under the railway. This pipeline was damaged by corrosion and it was necessary to evaluate its safety.

Stress-Deformed State of the Breed in the Funnel of Depression

Analytical solutions of one-dimensional equations of poroelasticity, describing the stress distribution in the depression (repression) funnel, are obtained in this work. It is shown that the influence of the boundary conditions on the wellbore wall is significant only in a relatively small (~1 m) vicinity of the wellbore bottom zone. It has been established also that in fractured rocks in cased wells, the compressive angular stresses, which largely determine the filtration conductivity of the bottomhole zones, will be less than in uncased wells. A method is described that makes it possible to increase the tightness of preserved wells in depleted fields. The method consists in cutting out a section of the casing pipe above the productive formation, expanding the wellbore in this section, installing a spring metal centralizer in this section, followed by cementing it. The formation of such a rigid element associated with the casing will prevent rock displacement relative to this pipe and ensure the tightness of the near-wellbore zone of the well.