Expandable Cement Research Articles

Biomechanical comparative evaluation of percutaneous fixations with vertebral expansion for vertebral compression fractures: an experimental and finite element study

This study uses in vitro experiments and validated finite element models (FEM) to analyze the effect of posterior fixation, alone or associated with expandable device (ED) and/or cement. 3-dimensional FEMs of intact, fractured and instrumented spine were built and compared with experimental load-displacement curves. FEM ranges of motion were within the experimental corridors. Stresses appeared sensitive to both implant configuration and fracture severity with a stress reduction up to 84%. The FEM highlighted that for a same instrumental strategy, different biomechanical performances were observed according to fracture severity. When bone continuity is altered, both ED and cement may be needed.

Novel Expandable Cement System for Prevention of Sustained Casing Pressure and Minimization of Lost Circulation.

Sustained casing pressure (SCP) is a common issue in the oil and gas industry. There were several solutions applied to contain it either by mechanical means or by injecting high-performing cement slurries. There are some limitations associated with these solutions such as volume loss, mechanical failures, limited expansion, exact spotting, and material deterioration with time. In this study, a novel expandable cement system contains a novel silicate aqueous alkali alumino silicate (AAAS) and zinc (Zn) metal slurry, and class G cement is introduced as an expandable solution to prevent annulus flow between the casing and formation. The silicate-based admixture reacts with the Zn metal slurry to generate hydrogen gas that results in the expansion of the cement slurry. The reaction and expansion can be controlled by optimizing the quantities of silicate systems and metal slurry. The expansive properties of the silicate system can be utilized to formulate a cement mix for plugging off the annulus flow. Cement slurries with different percentages such as 3, 5, and 8% by weight of water (BWOW) of AAAS silicate and Zn metal slurry were prepared and tested for their expansion. Several laboratory tests such as expansion, consistency, viscosity, and unconfined compressive strength were performed to assess the percentage expansion. The expansion was tested in the plastic tube as well as in expansion molds. The cement slurries were cured at 50 °C temperature in a water bath. It was observed that metal slurry upon reaction with AAAS silicate resulted in cement expansion by several percentages. The cement expansion was reduced by 16% at 8% BWOW concentration of AAAS silicate as compared to the expansion gained at 3% BWOW concentration. Further, the temperature triggers the expansion of cement slurry. The consistency and viscosity were impacted by the addition of AAAS and metal slurry. The application of expandable slurry can help in preventing the annulus flow and eliminating the safety issues associated with SCP. The expansion solution can be applied in loss circulation zones.

Development of non-shrinkable cement based on local raw materials

With an analysis of world practice in the production of non-shrinkable and expandable cement mortars and structures, the basic methods for their preparation are revealed. The main directions of their production are established based on the use of special expanding cements developed by various authors. An analysis of the above mentioned methods revealed that for the Republic of Armenia the most accessible method is the development of a special additive and its introduction into conventional Portland cement.Investigating the mineral base of the RA, a special additive was developed on the base of dust absorbed from exhaust gases of cement plants furnaces, by which it is possible to obtain non-shrinkable and expandable cements. Different ratios are determined at 800-1100 °C.The study revealed that at a ratio of 40:60 and 45:55 (gypsum: dust), the additive obtained at 1000°C contains a sufficient amount of ettringite, the main mineral for expansion. The expansion effects of the developed additives were studied, its optimal ratio corresponding to 10 percent by mass of cement was established.

Effect of expandable cement on increasing sealing ability of cement sheath in shale gas wells

The sustained casing pressure (SCP) problems in shale gas wells have not been effectively controlled by now. In field, the expandable cement sheath used in wells has decreased the SCP problems and in this paper, an analytical model is established to study how the expandable cement increases the sealing ability of cement sheath and give suggestions on optimized choosing of expandable cement. Meanwhile, the stress equilibrium state in well before cementing work which has not been considered in previous and it is considered in the analytical model here. During the curing process, the radial stress on the outer interface of cement sheath changes with time and increases much faster than it on the inner interface. In wells with single layer of casing, the radial stress on interfaces does not increase linearly with the cement elastic modulus (Et) and it will be affected by the elastic modulus of formation rock. In wells with double layers of casing, the expandable cement can significantly increase radial stress on interfaces during the production process and alters circumferential tensile stress into compressive stress which is useful for increasing the sealing ability of cement sheath. How the expandable cement increase the sealing ability of cement sheath in field has been analyzed and an optimized expand ratio of cement is proposed to control the SCP problems in shale gas wells.

Influence of the initial loaded state on the stress distribution of a wellbore system

Designing and maintaining the long-term integrity of an entire wellbore system is important to all its operations and to prolonging the service life of the oil and gas well. Some analytical or finite-element mechanical models have been built to calculate the stress distribution of the wellbore system, but most models ignored its loading history and took no account of its initial loaded state. Due to the shrinkage effect, nonexpandable cement systems likely induce tensile radial stresses on the cementing faces and aggravated cement-sheath failures, yet due to the expansion effect, expandable cement systems likely produced compressive radial stresses on the cementing faces and repressed cement-sheath failures. Now, more and more researchers have realized the importance to consider the initial loaded state. Some researcher have presented multistage methods to simulate the overall process before drilling, during drilling, and after drilling. However, because it is more complex and difficult to simulate the cement solidifying stage, some researchers tried to skip the simulation of cement solidifying process. To simplify the multistage method reasonably and accommodate the importance of the initial loaded state, we propose a new analytical mechanical model with a vertical wellbore and isotropic horizontal in-situ stresses. The model is derived according to the elastic mechanics theory, which can consider the loading history of the entire wellbore system and take account of its initial loaded state. The influences on stress distribution due to the initial state are discussed using a real-life example. We determined that considering the initial loaded state can cause substantial differences in the estimated stress distribution of the entire wellbore system. Taking the initial loaded state into account is essential for accurate design and examination of wellbore integrity.

Smart Expandable Cement Additive to Achieve Better Wellbore Integrity

One of the serious challenges encountered in cementing oil and gas wells is the failure of the cement sheaths and its debonding from casing or formation rock. Shrinkage of the cement during setting is identified as one of the driving factors behind these issues. Some expansive cement systems have been developed in the oil and gas industry to compensate for the shrinkage effect. All the expansive additives which have been developed so far have chemical reactions with the cement itself that would significantly impact the mechanical strength of the cement. In this paper, we present a new class of polymer-based expandable cement additive particles which are made of shape memory polymers (SMP). This class of polymers is designed to expand to the required extent when exposed to temperatures above 50–100 °C (122–212 °F) which is below the temperature of the cementing zone. It is notable that expansion occurs after placement of the cement but before its setting. The API RP 10 B-2 and 5 have been followed as standard test methods to evaluate expansion and strength of the cement slurry after utilizing the new additive. The proposed additive does not react with the water or cement content of the slurry. Mechanical evaluation tests confirm the potential benefit of this additive without any deteriorative effect on mechanical properties or setting time of the cement paste and significant impact on its mechanical properties. Hence, this additive would provide a reliable way to prevent cement channeling, debonding, and fluid migration to upper formations.

Cement Placement With Tubing Left in Hole During Plug-and-Abandonment Operations

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper IADC/SPE 178840, “Cement Placement With Tubing Left in Hole During Plug-and-Abandonment Operations,” by Bjarne Aas, Jostein Sørbø, and Sigmund Stokka, SPE, IRIS/DrillWell; Arild Saasen, SPE, Det Norske Oljeselskap; Rune Godøy, SPE, Statoil; øyvind Lunde, ConocoPhillips; and Torbjørn Vrålstad, SPE, SINTEF Petroleum Research/DrillWell, prepared for the 2016 IADC/SPE Drilling Conference and Exhibition, Fort Worth, Texas, USA, 1–3 March. The paper has not been peer reviewed. One way to reduce costs during plugging and abandonment is to leave most of the production tubing in the well. A major concern with such an approach, however, is whether the cement will displace the original fluid improperly because of lack of tubing centralization and possible unfavorable flow dynamics in the annulus. This paper presents full-scale tests that show it is possible to obtain good cement placement when the tubing is left in the hole. Introduction The fundamental goal of plugging and abandonment is to restore caprock functionality to maintain well integrity permanently. Normally, these operations are conducted by removing completion equipment and placing a series of cement plugs. One way to reduce costs is to leave most of the production tubing in the well, which would save significant rig time. A major concern with such an approach, however, is whether the cement has displaced the original fluid properly in the annulus outside the tubing where the plug is planned. Poor cement quality there may result from designing the original cement job with insufficient cement slurry, from a lack of tubing centralization, or from unfavorable flow dynamics in the annulus. Regardless of the equipment used for the operation, the most economical way is to leave as much of the tubing as possible in the well. If tubing can be left in hole in a way that satisfies long-term abandonment criteria, a significant restriction to cost-efficient plugging and abandonment is overcome. This paper presents full-scale tests that confirm the possibility of obtaining good cement placement when the tubing is left in the hole. This is the case both with and without control lines attached to the tubing. Experimental Equipment and Methods Full-scale tests, with several assemblies of 7-in. tubing cemented in 9 5/8-in. casing, were performed to determine the sealing ability of annulus cement when tubing is left in hole. Tests were performed with both conventional cement and expandable cement, and with and without control lines present. The quality of the cement placement was determined by pressure tests with water—where leakage rates and pressure drops over the test sections were recorded—and by visual inspection after cutting the test assemblies at different places.

Miniaturized Coiled-Tubing System Reduces Costs During Pipeline Decommissioning

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 175487, “Cost-Reducing Pipeline-Decommissioning Technology,” by Hugh MacKenzie and Callum Jones, Paradigm Flow Services, prepared for the 2015 SPE Offshore Europe Conference and Exhibition, Aberdeen, 8–11 September. The paper has not been peer reviewed. This paper presents the challenges and obstacles faced in the use of a new technology for the plugging and deoiling of sections of unpiggable flowlines before decommissioning. The solution used an ultralightweight, miniaturized coiled-tubing system that was deployable from the platform lower decks with minimal laydown area required. The system had the ability to traverse multiple bends, deoil the line, and deliver an expandable cement to plug the pipeline in a single operation. Introduction First production in the Murchison field began in 1980, and the field has now reached the end of its life. As part of the decommissioning project, one of the subsea wells was seen to be still connected to the Murchison platform by two flowlines contained within a subsea bundle (PL123), with these flowlines having 4-in. outer diameters. These lines were installed to provide early production for the first year until all the infrastructure was put in place. The control lines and pressure-monitoring system had been disconnected at the platform sometime in the past (Fig. 1). The bundle was inspected on the platform, and a hot tap was performed to identify any pressure in the lines and to identify the line contents. It was found that one of the two flowlines contained crude at a pressure of 122 bar. The pressure was reduced to zero, and the bleed line was closed with a gauge installed to monitor the pressure. It was noted that the pressure increased slowly over time. To continue with the decommissioning of the platform before the plugging and abandonment of the subsea well (211/19-2), PL123 had to be flushed of contents and a barrier had to be installed between the subsea well and the Murchison platform.

Cement Restrictor Function Below the Femoral Isthmus

Cement restrictors rely on achieving an interference fit with the wall of the medullary canal. Depending on the design of the cement restrictor, the intramedullary fit may be compromised as the femur starts to widen distally. Three different designs of cement restrictor were identified; universal, press-fit, and expandable. We determined which design of cement restrictor could resist the greatest pressures in a closed column of cement. Additionally, we recorded leakage of cement past the restrictor. We reamed synthetic femora to recreate the normal distal flare of the femur below the femoral isthmus. After inserting the cement restrictor, low-viscosity cement was gradually pressurized using an electronically controlled pneumatic ram. We then simultaneously recorded cement pressure above the cement restrictor and displacement of the cement restrictor. There was variation in the performance of the cement restrictors. The expandable cement restrictors resisted the greatest pressures. The resorbable expandable (REX Cement Stop) and press-fit cement restrictors reliably prevented cement leakage. The press-fit and universal restrictors failed at low pressures when deployed below the isthmus. The choice of cement restrictor may need to be modified if preoperative templating indicates the restrictor will sit below the femoral isthmus.

Insertion of an expandable cement restrictor reduces intramedullary fat displacement

The insertion of an intramedullary cement restrictor can lead to the same pathophysiologic reactions that are well described as fat embolism syndrome after cement and stem implantation. Fat and marrow are forced into the draining veins of the femur. In this study, we compared the extrusion of intramedullary contents produced by the insertion of a commonly used gelatin (Biostop G/IMSET) and a new expandable cement restrictor (REX Cement Stop) in 7 paired, fresh-frozen femora. A further 9 pairs were used to evaluate the function of a custom-made application instrument, which allowed for suction during plug (Biostop G/IMSET) insertion. The oversized restrictor produced, on average, twice as much fat as the expandable restrictor ( P = 0.0156). The gelatin plug with additional suction was not associated with reduced fat extrusion, because the suction device in its current design failed because of obstruction in most cases. The expandable restrictor showed favorable characteristics and has the potential to reduce the risk of fat embolism.

An assessment of borehole sealing performance in a salt environment

Design of plugs for abandonment of boreholes and shafts may be governed by the bond strength between the plug and host rock. This paper presents the results of push-out tests on cement grout plugs in salt. Two types of expandable cement grouts have been tested. The average interface shear strengths ranged from 2 to 12 MPa (290 to 1740 psi). Peak shear stresses at failure, assuming an elastic stress distribution along the interface, were up to eight times higher. Standard deviations commonly reached 20%. Dissolution along the interface was observed, and may have been enhanced by clay inclusions in the salt. This dissolution appears to have reduced bond strengths. Application of the results to the design of plugs for larger openings (for example, shafts, drifts, or boreholes) is discussed.