Materials Science Forum Vol. 847

Abstract: Shape memory polymer (SMP) is being studied and anticipated to be used in a novel down-hole packer. SMP is capable of recovering a predetermined shape following environmental changes, allowing the packer to be altered to a smaller size during run in and to retain its original configuration after activated by the heat in the wellbore. This paper describes the work involved in studying the shape recovery performance of a polyethylene based thermoresponsive SMP under different conditions. The influence of temperature, pressure and degree of deformation on the SMP’s shape recovery performance has been characterized.

Abstract: Casing wear is one of the key issues in the development of oil and gas fields and in the process of drilling operations. In this study, the relationship between hardness and wear resistance of drill collar and casing was studied; thereby the wear conditions between the two materials were improved. Chemical analysis, optical microscopy, hardness test and friction wear test were conducted to study the effects of heat treatment on hardness of the drill collar 4145H and the casing 30Mn5V, and discuss the relationship between hardness and wear resistance of them. The results showed that the materials of drill collar and casing after different heat treatment had varying degrees of wear, both of the respective wear amounts were gradually increasing with the increase of hardness of them, the wear extent of casing material was greater than that of drill collar material. The hardness of casing material was the lowest and its wear resistance was the best when quenching at 880°C and tempering at 630°C. And when quenching at 900°C and tempering at 690°C, the hardness of drill collar material was the lowest and its wear resistance was the best. Therefore, the hardness of drill collar and casing can be improved by changing the heat treatment process to improve the wear resistance, thereby reducing the wear conditions between them.

Abstract: In this paper, the corrosion tests of glass fiber reinforced polymer (GFRP) in high temperature and high pressure acid environment were carried out. The surface morphology and glass transition temperature were observed by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and the mechanical property of GFRP was tested. The results indicated that after being exposed to acid corrosion environment, the structure and organization of GFRP changed, and a variety of defects produced on the surface and interior of GFRP, bending strength and tensile strength of GFRP decreased. The surface analysis also proved that there were some etch pits occurred on the GFRP pipes. Furthermore, their barcol hardness became poor.

Abstract: In-service welding of the pipeline steel is performed under the environment where the delivery of the high pressure pipeline doesn’t stop. When welding under the water, there are high-pressure gas flowing in the pipeline and water flowing outside, causing a difficult and possibly risky of the welding operation. The process of in-service welding with SYSWELD was adopted to establish a geometric model of pipeline repair that the pipeline steel using finite element numerical modeling of the underwater in-service welding was carried out. Furthermore, this study focused on the effect of water velocity on the temperature field and stress field when repairing the in-service pipeline by welding. The results indicated that the water velocity of the pipe has a great influence on the temperature field and the residual stress field.

Abstract: In view of the common polymer retarder of AMPS has poor sedimentation stability for slurry in high temperature, and thickening curve for unusual problems, a new terpolymers retarder PSIH which can solve the problem for the large temperature difference was synthesized by free radical aqueous solution copolymerization using styrene sulfonate (SSS), Itaconic acid (IA) and unsaturated hydroxyl ester monomers X . The structure and thermal stability of the copolymer was characterized with gel permeation chromatography (GPC), infrared spectroscopy (IR), and thermal gravimetric analysis (TG). The application performance of the retarder was assessed. The results demonstrated as follows. 1) The preferred synthesis conditions of the retarder is: the mass ratio of SSS/IA/X=9: 3: 1, temperature=60°C, initiator concentration =2%, the reaction time=5h, pH value was controlled in the neutral bias acidity. 2) Synthetic copolymer is the target product with appropriate molecular weight and has good thermal stability with thermal decomposition temperature of the main chain up to 375°C. 3) Compared with ordinary retarder the PSIH has merits as follows: excellent thermal resistant ability and sedimentation stability in high temperature; the rapid development of compressive strength in low temperature, and a big temperature span (30 °C~150 °C). The thickening time of the slurry with 1.0% PSIH is 245 min at 150°C; the compressive strength of cement with the same dosage can get up to 4.7MPa at 30 °C. In short, PSIH has excellent ability to cope with large temperature difference, providing a strong technical support for complex deep well cementing.

Abstract: With the exploration of oil and gas in depth, shallow wells already can’t satisfy the requirement, therefore to explore and develop deep reservoirs is necessary. In the case of deep wells the loop temperature of bottom can reach to 150°C-200°C, which put forward a higher requirement for the high temperature resistance property of cement slurry. At present, many problems existed in the most of high temperature cement slurry. For example, high temperature resistance is not well, cement thickening time can’t adjust easily, mega-thermal sedimentation stability is unsatisfactory, and ultra-retarding phenomenon appeared for the top prone. After research indoors, we developed the ultra-high temperature slurry system by means of the investigation on cementing additives and select proper materials from high temperature resistant fluid loss additives, retarders, flowable agent at the same time. This system needs a lots of properties, such as, adjustable slurry thickening time below 200°C, great slurry sedimentation stability, API loss can be controlled at the range of 0-50ml, insensitive to temperature and density, could be used in low-density and conventional density cement etc. This system be used successfully in the well that loop temperature of bottom reaches to 185°C and get a good effect finally.

Abstract: The effect of CO₂ on the hydrogen permeation behaviour of carbon steel was investigated in a high temperature and high pressure hydrogen permeation device, through hydrogen permeation test, weight loss test, hydrogen content test, and SEM-EDS. The results showed that the peak value of the hydrogen permeation curves were almost the same with or without CO₂, but the hydrogen permeation curve rose sharply, and then decreased gradually to a stabilized current value in H₂S/CO₂ environment, which was lower than in H₂S environment. The corrosion rates and the amount of hydrogen of steel in H₂S/CO₂ environment were lower than in H₂S environment. Therefore, it is considered that CO₂ has an effect on the hydrogen permeation in H₂S, mainly due to the change of corrosion products.

Abstract: On account of that the domestic polymer fluid loss additive exists some severe problems, such as, inferior thermal resistance, poor salt tolerance, strong shear-and thermal thinning behavior, a novel polymer/silica nanocomposite PADMO-V@NS is used as ultra-high temperature fluid loss control additive for cementing. In the present study PADMO-V@NS was prepared through an in situ free radical copolymerization of 2-acrylamico-2-methylpropane sulfonic acid (AMPS), N,N-dimethylacryl amide (DMAM), maleic anhydride (MA), octadecyl dimethylallyl ammonium chloride (ODAAC) and triethoxyvinylsilane (VTS) modified nanosilica. The linear hydrophobic associated copolymer was regarded as the shell and the modified nanosilica as the core. The microstructure, compositions and thermal resistance of PADMO-V@NS were investigated through FTIR and TGA techniques. The results showed that the copolymer modified with nanosilica particles possessed more excellent thermal stability than that of PADMO, and the most rapid decomposing temperature of PADMO-V@NS was highly up to 396.9°C. The application performance of PADMO-V@NS in cement slurry exhibited that it had excellent fluid loss control capacity, good high temperature resistance, strong salt tolerance and mild shear-/ thermal thinning performance, and could be used in 220°C and saturated brine circumstances. Moreover, comparing to PADMO, the compressive strength of set cement containing the copolymer increased over 20 % at 80°C, atmosphere pressure and curing time of 1 day due to the reaction of residual silanol groups with Ca (OH)₂. The laboratory research results indicated that the multi-functional fluid loss additive composed of hydrophobic associated polymer/silica nanocomposite had bestowed on the cement slurry systems good comprehensive properties, and may have extensive applications in deep & ultra-deep oil/gas wells cementing.

Abstract: A dissolvable material used in oil/gas field was introduced. The corrosion property of the dissolvable material was characterized by using immersion method and scanning electron microscope. The dissolvable material could quickly react with KCl solution, and the reaction rate improved with the increase of the temperature. In some cases, the downhole tools made by dissolvable materials should not react with well fluid in a short term. Then a protective multilayer coating was fabricated on the material surface. The protective effect of the coating was evaluated with high temperature immersion method. The results indicated that the coating could effectively inhibit the dissolvable material reacting with KCl solution.

Abstract: During shale gas well drilling and completion, the oil based muds (OBMs) would reduce the bonding strength of cement slurry by filter-cake and oil-wettability. At the same time, mixing cement slurry with the OBMs can lead to contamination, and subsequently creates significant problems, such as, reducing the normal thickening time and the compressive strength, and hence affecting the quality of the cementing of the shale gas well. Therefore in the present investigation, the mechanism of the interface displacement, wetting conversion and the contamination was explored by Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), scanning electron microscope (SEM) and other methods. And then the new materials with the enhanced bonding strength and the contamination relieving by OBMs were obtained. The results showed that the chemical composition of filter-cake determined the properties of chemical preflush, the combined systems (LSS) efficiently flushed filter-cake and increased the bonding strength. It has been found that the reverse wetting agent (APG) has better reverse wetting properties than Tarim Oilfield current application system, which effectively changes the wettability of cementing surface from lipophilicity to hydrophilic. The OBMs and cement slurry mixing generated the emulsion structure and honeycomb structure, and the structures can affect the rheology and the strength of cement slurry; the contaminative relieve agent (SCW) can form a thin film on the surface of the cement stone, the film covers the hole and improves cement compressive strength, thus the SCW can relieve the contamination by OBMs.