Resin Consolidation Research Articles

Model-Based Optimal Control of Polymeric Composite Cure in Autoclave System

The fabrication of high loaded aircraft polymeric composite parts requires tools such as heated closed-mold to which a pressure is applied at the correct gelation stage of the resin. The curing process includes the placing of a premixed compound in the mould, a pre-warming to the resin viscosity reaches a minimum, next applying of pressure to remove the gas bubbles and excess resin, and finally consolidation of resin at elevated temperature to its full polymerization. During matched-die molding, at which the mould is heated by the pressurization gas inside an autoclave or by built-in electrical resistance elements, it is particularly important that pressure is applied at the correct gelation stage of the resin within the cured body. To match the independently controlled pressure and mould heating we propose a model-based control approach, which use the mathematical model for epoxy-based thick-walled composite structure cure in the form of coupled kinetic equation of the resin with the heat transfer equation. This model takes into account an exothermal heat, change of the heat capacity and heat transfer coefficient at the phase transition of resin from liquid to gel and further to the solid state, where warmed pressurized gas in autoclave should provide the most uniform temperature field within the cured composite body. We formulate the control law for the inward heat flow as a function, which depends on four parameters determined at the solving of the optimization problem. To optimize this control law we restore the Pareto frontier for the minimized standard deviations of degree of cure and temperature averaged over the cured body. Finally, we compare the abilities to ensure the high quality curing results in the closed moulds heated by autoclave and by the discrete set of heaters positioned along the length of the die.

Experimental Investigation About Stamping Behaviour of 3D Warp Interlock Composite Preforms

Forming of continuous fibre reinforcements and thermoplastic resin commingled prepregs can be performed at room temperature due to its similar textile structure. The “cool” forming stage is better controlled and more economical. The increase of temperature and the resin consolidation phases after the forming can be carried out under the isothermal condition thanks to a closed system. It can avoid the manufacturing defects easily experienced in the non-isothermal thermoforming, in particular the wrinkling [1]. Glass/Polypropylene commingled yarns have been woven inside different three-dimensional (3D) warp interlock fabrics and then formed using a double-curved shape stamping tool. The present study investigates the in-plane and through-thickness behaviour of the 3D warp interlock fibrous reinforcements during forming with a hemispherical punch. Experimental data allow analysing the forming behaviour in the warp and weft directions and on the influence of warp interlock architectures. The results point out that the layer to layer warp interlock preform has a better stamping behaviour, in particular no forming defects and good homogeneity in thickness.

Optimization of the Composite Cure Process Based on the Thermo-Kinetic Model

High performance composite structures produced by the processes at which the consolidation of the fibres and matrix is done at the same time as the component is shaped. Full curing schedule include a pre-warming for resin liquefaction, next apply of pressure to remove the gas bubbles, and finally consolidation of resin at elevated temperature to its full polymerization. The change in the state of the composite should be made as possible uniformly across the thick-walled products. The complexity of process control is due to unobservability of the rheological state of material in a closed volume of a mould. In this paper we propose a mathematical model of epoxy-based thick-walled composite structure curing. PDE system linking a kinetic equation of the resin cure with heat transfer equation, take into account a phase transition from liquid to gel and further to the solid state. On the basis of transient analysis of the developed model we optimize the temperature control law.

Techbits: Slimhole Sand Control Evaluated at Malaysian Workshop

Techbits Remedial and slimhole sand control completions took center stage at a recent SPE Advanced Technology Workshop (ATW) held in November 2008 in Penang, Malaysia. Titled "Chasing Lost Reserves with Remedial and Slimhole Sand Control," the ATW reviewed methods for maximizing recovery of reserves in place by using economical through-tubing and slim-hole sand control technologies. Over the course of three days, 64 participants from 25 different organizations and 11 countries reviewed state-of-the-art sand control technology and recent technical advancements. They also benefited from the experience of other operators who shared case histories and established a network for information exchange with fellow participants. Cochairpersons Michael Bailey (Drilling and Completions Engineer with ConocoPhillips) and Raymond Tibbles (Stimulation and Sand Control Adviser, Middle East and Africa, for Schlumberger), opened the ATW with an overview of the goals and objectives for the workshop. They encouraged all attendees to participate with any lessons learned from sand control technologies that they had applied. This was followed by the keynote address by Haji Kamaludin Bungsu, Asset Manager (Western Asset), Brunei Shell Petroleum (BSP) Company. Bungsu's speech provided an overview of the reserves recovery challenges facing operators in the region, with particular emphasis on the cost and time required to develop new assets and the need to recover the maximum amount of reserves from existing developments. He then discussed the problems associated with brownfield sand production, either due to failure of primary sand control or late-time formation failure when no sand control was installed. He finished with a list of some of the options BSP was exploring to address these issues, while reiterating the need for more and better tools for later term sand remediation and better working relationships between operators and service companies. The first technical session was a discussion on the economic drivers for remedial sand control and the need to think about a well's entire productive life during the initial design phases. An overriding message was how initial completion choices drive the decisions for the rest of the well life and how some simple changes can produce a significant impact. One example detailed how increasing the size of slimhole completions from 3.5 to 4.5 in. can create many more remedial possibilities at lower risk. The next two sessions reviewed the various techniques available for through-tubing and slimhole sand control. Discussion topics ranged from resin consolidation and screenless fracture packs to through-tubing gravel packs, vent screens, and expanding tubular applications. In addition to discussing the techniques themselves, much time was devoted to weighing the risks associated with these techniques and their impact on productivity.

Consolidation of U-Nyte® Epoxy-Coated Carbon-Fiber Composites via Temperature-Controlled Resistive Heating

Temperature-controlled internal resistive heating creates on-command rigidizable materials for structural consolidation of ultra-lightweight, inflatable space structures. A PAN-based carbon fiber tow coated with a novel, low cure-temperature thermosetting resin (Hydrosize U-Nyte® Set 201 epoxy binder) was investigated for consolidation through internal resistive heating. Precise, proportional-integral (PI) temperature tracking was achieved for controlled sample heating and used to prescribe intelligently-designed curing profiles to cause resin consolidation and curing. Rigidized samples were evaluated by measuring the increase in bending stiffness as well as verifying resin cure completion through DSC. The permanent strength gained through active rigidization via internal resistive heating was demonstrated on a small, inflatable structure.

Effects of Resin Consolidation on the Durability of IM7/PETI-5 Composites

An experimental study was undertaken to investigate the mechanical response of the graphite fiber reinforced thermoplastic polyimide composite IM7/LaRC™-PETI-5 for use in long term durability tests. Composite panels were prepared using unidirectional prepreg and regions of different resin consolidation were identified using a nondestructive ultrasonic technique. Specimens representing four different degrees of resin consolidation were tested at room temperature in tension, compression, and flexure in the as-received state, as well as isothermally exposed for 1500 h at 177°C, and isothermally exposed to a “hot/wet” environment (80°C, 90%+ relative humidity). Results showed that specimens tested in tension and compression had a higher dependence on resin consolidation than those tested in flexure. However, specimens tested in flexure showed a greater property degradation from environmental exposure due to a lack of resin consolidation.

Using Local Gravel to Control Sand Production in a Saudi Oil Field

Sand production from oil and gas reservoirs is most commonly associated with unconsolidated and poorly cemented sandstones. Sand production problems are encountered throughout the world and recently are detected in Saudi Arabia. Several techniques could be used to minimize sand production such as drawdown control, installing screen liners, applying resin consolidation, gravel packing, etc. This work was conducted to investigate the possibility of using gravel packs made from gravel deposited in the central province of Saudi Arabia. Optimum gravel size, shape, crushing resistance and solubility in acids were tested. The results of the above analysis showed that the selected Saudi gravel properties meet the recommended API requirements. Furthermore, a physical model has been constructed to simulate sand control process. This model was used to study the effect of drawdown pressure, confining pressure and gravel-pack thickness on rate of fluids and sand production in a Saudi oil field. The experimental results showed that sand and fluid production are affected by the gravel pack thickness, drawdown pressure and confining pressure. Therefore, it is recommended to utilize the tested Saudi gravel in sand control applications after performing an economical feasibility study.

Tow Collapse Model for Compression Strength of Textile Composites

The unidirectional composite compression strength model based on microbuckling of fibers embedded in a rigid-plastic matrix was extended to multiaxial laminates and textile composites. The resulting expression is a function of matrix yield strength under the fiber constraint, fiber tow inclination angle, fiber volume fraction, and the area fractions of various sets of inclined tows. The analysis was verified by experimentation. Compression tests were conducted on laminated, three-dimensional triaxially braided and orthogonally woven composites using the IITRI test specimen. The laminate specimens were made up of AS4/3501-6 graphite/epoxy composite with (0)24, (0/30/0/ - 30)35, and [(0/90)6/0)]s stacking sequence. Textile composites were made of BASF G30-500 graphite fiber tows (tow size is 6K) and Dow Chemicals Tactix 123 matrix. Fiber preform architecture of braided and woven composites before resin consolidation was 0/ + 17 and 0/90, respectively and after consolidation it was about (7/ + 20) and (5/90/90), respectively. The analysis agreed reasonably well with the test data for all cases considered. The axial fiber/tow misalignment angle for laminated, braided, and woven composites were about 4, 7, and 5 degrees, respectively. The compression strength was found to be strongly dependent on the percentage of axial tows and its misalignment angle. A small variation in the off-axis fiber/tow orientation had marginal effect on the compression strength. Hence, the off-axis tow misalignment angle can be assumed to be same as the initial laminate or the tow orientation angle.

Perforating Resin-Consolidated Zones for Capacity Improvement

Sand control using epoxy resin consolidation usually is effective, but treated wells fail to produce occasionally. This, paper presents field results showing that through-tubing jet reperforation of wells into the previously resin-consolidated zone can restore production. previously resin-consolidated zone can restore production. Laboratory tests indicated clean, productive perforations and undamaged resin consolidation. Introduction Reservoirs from surface to 8,000 ft and deeper off the Louisiana coast are notorious sand producers. Excessive sand production can result in separation and disposal problems, erode pipe and equipment, damage casing, problems, erode pipe and equipment, damage casing, and shutdown pumps. Sand control is necessary in wells of this type. From 1958 to 1972, when multiple completions were most common, Chevron Oil Co. elected to complete many wells dually with two-stage gravel packs in lower zones and resin consolidation in upper zones. Any selective (single) zones also were resin consolidated. Both sand control methods have proven highly successful. However, in several instances some resin-consolidated zones failed to produce, and acidizing also failed to induce flow. Assuming sand or mud fillup is not blocking the perforations, it has been proposed that unintended dirt or debris injected with the resin and associated fluids may plug perforations or damage near-well formation plug perforations or damage near-well formation permeability. permeability.After all other methods failed to induce flow from these wells, reperforation with through-tubing, jet-perforating guns gave promising results. Field Work Six nonproducing or low-production resin-consolidated wells were reperforated. Two other selected wells were not reperforated because of mechanical problems encountered. The selected wells are located east of the Mississippi River delta in the Main Pass area. The productive section is Upper Miocene in age, with sands and productive section is Upper Miocene in age, with sands and shales deposited in a near-shore marine environment. As the electric logs (Fig. 1) suggest, some sands are massive and relatively clean with porosities of 30 to 35 percent, while others are argillaceous with lower porosity. The eight wells represented two different types of completion. One was the selective zone completion (Fig. 2). Casing was perforated, sand was resin consolidated and packers were placed on single tubing string, isolating the zones at initial completion. Only one zone was produced at a time, starting at the bottom and progressing up produced at a time, starting at the bottom and progressing up the tubing. When moving to an upper selective zone, lower zones were plugged off and a special tubing perforator was used to open the tubing between the packers perforator was used to open the tubing between the packers isolating the selective zone to permit flow. In contrast, when using the reperforation completion technique, the reperforating gun in a selective zone must perforate both tubing and casing. A through-tubing, expendable, capsule-type, jet perforating gun was used. Shot density was four shots per foot, oriented at a 90 degrees angle. Wells 1 and 2 were selective zone completions. The second type was the standard dual completion (Fig. 3). Two strings of tubing allowed simultaneous but separate production from both zones. In our examples, only the upper zone was resin consolidated. To reperforate these zones, the perforating gun was lowered through the short tubing string until it hung free in the upper zone. Only the casing was penetrated. JPT P. 283