|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
A number of cementitious materials used for cementing wells do not fall into any specific API or ASTM classification.These materials include: Pozzolanic materials include any natural or industrial siliceous or silico-aluminous material, which will combine with lime in the presence of water at ordinary temperatures to produce strength-developing insoluble compounds similar to those formed from hydration of Portland cement. Typically, pozzolanic material is categorized as natural or artificial, and can be either processed or unprocessed. The most common sources of natural pozzolanic materials are volcanic materials and diatomaceous earth (DE). Artificial pozzolanic materials are produced by partially calcining natural materials such as clays, shales, and certain siliceous rocks, or are more usually obtained as an industrial byproduct. Pozzolanic oilwell cements are typically used to produce lightweight slurries.
Remedial cementing requires as much technical, engineering, and operational experience, as primary cementing but is often done when wellbore conditions are unknown or out of control, and when wasted rig time and escalating costs force poor decisions and high risk. Squeeze cementing is a "correction" process that is usually only necessary to correct a problem in the wellbore. Before using a squeeze application, a series of decisions must be made to determine (1) if a problem exists, (2) the magnitude of the problem, (3) if squeeze cementing will correct it, (4) the risk factors present, and (5) if economics will support it. Most squeeze applications are unnecessary because they result from poor primary-cement-job evaluations or job diagnostics. Squeeze cementing is a dehydration process.
Abstract Monobore cementation is defined as where a single production tubing size runs from the pay zone all the way to surface and is cemented in place. This type of well design greatly reduce rig time and cost. The challenge however is to achieve a good cement in the annulus as a well barrier and to have a clean internal tubing after the cementing job to allow for successful production of the well. To achieve a clean internal tubing, a distinct bottom and top plugs were used as a means of mechanical separation. For fluids design, mud had to be thinned down prior to the cementing job and, a designed fiber based spacer system was used to physically scrub any mud-film sticking on the tubing walls. The centralizers and cement system were designed to allow for efficient displacement of mud and hence providing good overall placement and top of cement in the tubing-casing annulus. The cement in the annulus will be verified by pressure testing the annulus to 500 psi higher than previous shoe leak-off. This approach was implemented for the campaign of six wells, all designed with 5-1/2in monobore tubing. The bottomhole static temperature (BHST) of the well ranges from 300 to 350°F. The cementing system also had to be designed to cater to the challenge of this field, having CO2 as high as 60%, high temperatures, and a long open hole section that requires isolation and cement to set within a required timeframe. The cementing jobs were validated by no losses or gains during the job, floats holding at the end of the cementing job, differential pressure of cement prior to bumping the plug, density and pump rates executed as planned, accepted pressure test criteria of the annulus, output validation of cement contamination in pipe and annulus based on fluids and final well information. To further validate this system, the cement bond log was also run as part of the evaluation process and the cement log showed that zonal isolation was achieved. After the perforations, the perforation tool was pulled out to surface and the tool looked very clean with no signs of contaminated mud or cement around the tool. We demonstrate how this unique cementing approach can be a solution for the challenges of monobore cementing and one of the biggest problems of monobore cementing in the industry.
The table also includes an indication of the primary uses and benefits, along with the cements that they can be used with. The primary effects of the cement admixtures on the physical properties of the cement, either as a slurry or set, are presented in Table 2. This is a quick reference, and individual additives in a given category may not agree in total with the effects as given. It is also typically defined for individual additives, the properties and effects of which can be modified when additive combinations are used.
Almost all drilling cements are made of Portland cement, a calcined (burned) blend of limestone and clay. A slurry of Portland cement in water is used in wells because it can be pumped easily and hardens readily, even under water. It is called Portland cement because its inventor, Joseph Aspdin, thought the solidified cement resembled stone quarried on the Isle of Portland off the coast of England. Portland cements can be modified easily, depending on the raw materials used and the process used to combine them. Proportioning of the raw materials is based on a series of simultaneous calculations that take into consideration the chemical composition of the raw materials and the type of cement to be produced: American Society for Testing and Materials (ASTM) Type I, II, III, or V white cement, or American Petroleum Institute (API) Class A, C, G, or H.  The basic raw materials used to manufacture Portland cements are limestone (calcium carbonate) and clay or shale.
The first step in designing a gel treatment is to correctly identify the nature of the conformance problem to be treated. This includes, during water- or gas-shutoff treatments, identifying the flow path of excessive water or gas production from its source to the production wellbore. The following procedure for gel technology selection is highly generalized, and the procedure should be modified as dictated by the actual reservoir conformance problem to be treated. If a service company or a company specializing in conformance treatment gels is to be involved, they should be consulted during each step of the selection process. A prerequisite is to eliminate all gel technologies, if any, that are prohibited by locally applicable safety or environmental regulations. First, determine the type of problem that is to be treated. That is, whether it is a matrix-rock problem or a high permeability anomaly problem, such as fractures.
Cementing is an essential part of the oil well and with deeper wells drilled, the performance of cement decides the life of the well even more critically. Cement undergoes many changes from the time it is mixed on the surface and pumped downhole and allowed to set. The varying temperature changes from surface to downhole along with the exothermic reaction of the setting cement creates a complex series of events which decides the fate of the well. With the advent of new technology and research cement performance has been improved several folds. An essential part of oil well drilling today, cement had a very humble beginning.
Surface formations in the Arctic, called permafrost, may be frozen to depths in excess of 2,000 ft. In addition to addressing concerns about the freezing of water-based fluids and cement, the engineer must also design surface casing for the unique loads generated by the thawing and refreezing of the permafrost. There are also road and foundation design problems, associated with ice-rich surface permafrost, that are not addressed here. The following is a qualitative description of the loading mechanism in permafrost. If we consider a block of permafrost before thaw, the overburden and lateral earth pressures surrounding this block are balanced by the intergranular stresses between the soil panicles and the pore pressure in the ice.
Someehneshsin, Javad (Memorial University of Newfoundland) | Quana, Weizhou (Memorial University of Newfoundland) | Abugharara, Abdelsalam (Memorial University of Newfoundland / Sebha University) | Butt, Stephen (Memorial University of Newfoundland)
ABSTRACT Exploiting very thin but valuable ore bodies that are uneconomical to extract by conventional mining methods is being noticed nowadays. Some methods are used to mine stranded, steeply dipping ore veins which are too small or isolated to mine economically using conventional methods since the dilution is minimized. This novel mining technique uses drilling rigs to extract the ore through directional drilling surgically. This paper is focusing on utilizing the run of the mine tailings and Portland cement as backfill material to support the hanging wall for providing safe mine operation and different methods, including Marston's theory and Terzaghi's theory, for calculating freestanding vertical face were proposed and compared. Also, the arching effect and inclination of stope were considered. Cemented paste backfill (CPB) is designed by mixing waste tailings, water, and cement of the precise percentage for optimal outcomes. It is a non-homogenous material that contains 70–85% solids.The vertical normal stress for a 2 meters diameter and 200 meters depth hole, filling with 2000 kg/m waste tailings, will be 0.123 MPa and using a backfill material with 1 MPa compressive strength is suggested. 1. INTRODUCTION One of the most important tasks of the post-mining process is mine backfilling. Typically, backfill is made of soil, overburden, mine tailings or any other kind of aggregate which can be used as a filler and booster in the extracted area which was excavated by mining operations. Backfill material is placed into previously extracted stopes to produce a stable platform for the miners to work on, and provide ground support for the walls of the adjacent adits while mining progresses. These backfills reduce the amount of open area that might be filled by a collapse if the encompassing pillars failed (Barret et al. 1978). Backfill material is categorized as hydraulic fill, paste fill, and rock fill. In order to increase the strength of the backfill material, a small amount of binder (Portland cement) is added to the mixture. Mine productivity could be enhanced by using underground paste backfill. Paste backfill not only supports the ground for the pillars and walls, but also helps stop caving, roof collapse, and improves pillar recovery (Coates 1981).
Abstract After drilling each section of a well, cement is placed in the annulus of the casing and the formation. The cement integrity must be ensured during the life cycle of the well or after abandonment. If for any reason, the cement lost its integrity, the consequences could be severe for personnel, equipment, and the environment. When the cement fail, leakages may occur through the cement pathways and sealant materials are used to plug these pathways. This study investigates a temperature activated epoxy resin sealant to evaluate the potential use of this sealant as an alternative to Portland cement in oil and gas wells. This study focuses on analyzing the rheological behavior of the sealant, the effect of temperature on the rheology and the curing time of the sealant, the penetrability of the sealant into small voids, and the blocking efficiency of the sealant. Experimental tests were conducted to evaluate the epoxy resin sealant including rheological measurements, density, injectivity, blocking efficiency, and mechanical properties. The findings of this study show that this sealant has low viscosity and Newtonian rheological behavior, low density as low as water, high injectivity and penetrability even in small gaps, ability to resist differential pressure higher 1000 psi, and extremely high compressive strength. This work demonstrates that epoxy resin sealant can be used effectively and safely in sealing cement voids.