Lian, C. J. (Shandong University of Science and Technology) | Hou, J. Z. (Shandong University of Science and Technology) | Gao, G. L. (Taian Taishuo Strata Control Science and Technology Co. Ltd.) | Wang, G. (Taian Taishuo Strata Control Science and Technology Co. Ltd.) | Song, W. T. (Henan Polytechnic University)
ABSTRACT: It has wide distributions and large recoverable reserves of Jurassic period coal seam in China. It is difficult to maintain stability of the development roadways with long service term for Jurassic strata because there are abundant argillaceous rocks and some minerals in the high argillaceous rocks will be expanding while meeting with water. The fractures of the roadways develop well under high stress and are suitable to filling with grouting. But the poor cementing performance of cement with argillaceous rock as well as a heavy water filtration rate of cement slurry had resulted in failures of many engineering cases adopting cement grouting to reinforce this kind of roadways. In this paper, according to characters of the high argillaceous rock in Jurassic strata, a marlaceous inorganic grouting material which possesses the well cementing performance with argillaceous rocks and little filtration rate was introduced; and the grouting reinforcement mechanism, construction technique and engineering application effect about it was clarified. It will be of great significance for reinforcement and maintenance of the development roadways with high argillaceous rocks.
According to statistics, 60% of the proved coal reserves in China distributes in Early-Middle Jurassic period of northern North China, southern Northeast China and Northwest China, along with late Jurassic to early Cretaceous period of Northeast China and east Inner Mongolia. The period of coal forming is short and argillaceous rocks are abundant in Jurassic strata. Moreover, there are quite a few expanded minerals in some strata. So the roadways are easily to be deformed and damaged when affected by mining-induced stress. In addition, this kind of soft rock roadways has an obvious time effect. For the development roadways with long service term, serious deformations are frequently observed and part of the roadways has suffered deformation and maintenance time after time. The stability support of the development roadways really need much cost.
The successful exploitation of tight-gas reservoirs requires fracture networks, sometimes naturally occurring, often hydraulically stimulated. Borehole microseismic data acquired in such environments hold great promise for characterising such fractures or sweet spots. The loci of seismic events delineate active faults and reveal fracture development in response to stimulation. However, a great deal more can be extracted from these microseismic data. For example, inversions of shear-wave splitting data provide a robust means of mapping fracture densities and preferred orientations, useful information for drilling programs. They can also be used to track temporal variations in fracture compliances, which are indicative of fluid flow and enhanced permeability in response to stimulation. Furthermore, the frequency-dependent nature of shear-wave splitting is very sensitive to size of fractures and their fluidfill composition. Here we demonstrate the feasibility of using such analysis of shear-wave splitting measurements on data acquired during hydraulic stimulation of a tight-gas sandstone in the Cotton Valley field in Carthage, West Texas.
This paper presents the results of laboratory investigation about fatigue of Class G wellbore cement exposed to radial loads under room temperature conditions.
While fatigue is well described for metals, wellbore cement fatigue is a rather unknown field. As well cements can be exposed to cyclic loading situations like in new oilfield technologies e.g. enhanced oil recovery by steam injection or geothermal applications using single-well-solutions, cement damage by fatigue becomes a more important issue. Cement integrity is crucial environmental and economic issue and no risk on cement failure should be accepted. The thermal induced loads in the reality were replaced by mechanical loads that recreates the stress situation on the cement. In order to evaluate the behavior of the cement, experiments were performed to investigate how cement reacts to cyclic loadings. A low number of cycles mean up to 100 loadings sequences. Samples of a pipe-cement-compound recreating the wellbore geometry are tested in a hydraulic press under axial loads. The stress situation in the cement sheath of the tested samples was calculated using a combination of numerical and analytical methods. Failure criteria were used to evaluate these calculations and could be used to predict future failure behavior. It has been found that fatigue of cement is rather similar for metal and cement at least in the low cycle range. For metals there is a specific stress limit where failure or significant damage to the material occurs within several cycles. This means, if the limit is exceeded the material will fail, maybe not at the first cycle, but it will fail over the cycles. Cement shows that this behavior is similar to metals, no other fatigue mechanisms like damage accumulation were observed, just a straight load limit.
ABSTRACT Reinforced concrete pipes are commonly used for culvert and storm drainage applications and are intended to last for several decades. The effect of cracks on corrosion of embedded reinforcing ~3/16 in (~4.75 mm) diameter steel wires was investigated. Cracks having a nominal width of 0.02 and 0.1 inch (~ 0.5 and ~2.5 mm) were induced by 3-point bending on the interior surface of quadrants extracted from 18inch (45 cm)-diameter concrete pipes. Two types of concrete pipes were examined and referred to as Z-type and R-type with average interior concrete covers of 1.2 and 0.7 inch (30.5 and ~17.8 mm) respectively. The Z-type contained higher cement content whereas the R-type had a 20 % fly ash replacement. The cracked specimens along with controls were tested under both continuous and 1 week-dry/1 week-wet cyclic exposures to 500 ppm chloride solution for periods of 115 days and 7 cycles respectively. Open circuit potential and electrochemical impedance measurements were performed. Electrochemical test results were calibrated using data obtained from destructive examination of wire corrosion. Data analysis showed that corrosion current increased as the crack width-to-cover ratio increased for both types. Corrosion-based projection models indicated strongly enhanced performance for the 0.02-inch (~0.5 mm) cases compared to the 0.1-inch (~2.5 mm) cases. INTRODUCTION Reinforced concrete pipes (RCP) are widely used in installations requiring service over a period of many decades, so only extremely slow deterioration with time can be accepted. Concrete cracks are often revealed by inspections conducted on recently placed pipes. In-place RCP cracks can degrade pipe performance by decreasing structural strength and dimensional stability, permitting leaks and marginally increasing hydraulic resistance, and by allowing premature corrosion of steel reinforcement.1- 3 At the bottom of such cracks bare steel is likely to be directly exposed to water which, if renewed regularly by flow, would eventually have a pH close to that of the environment.
Song, Fengmei (Southwest Research Institute) | Lu, Baotong (Southwest Research Institute) | Elboujdaini, Mimoun (CANMET Materials Technology Laboratory Natural Resources Canada –) | Gao, Ming (Government of Canada)
Saithala, Janardhan Rao (GL Noble Denton) | Mahajanam, Sudhakar (ConocoPhillips) | Rincon, Hernan (ConocoPhillips) | Clapp, John (ConocoPhillips) | Ubhi, Harvindher Singh (Oxford Instruments HKL A/S) | Atkinson, John D. (Engineering Department Sheffield Hallam University)
Piccolo, E.Lo (Centro Sviluppo Materiali SpA) | Nice, P.I. (Statoil ASA) | Fattnes, O. (Statoil ASA) | Morana, R. (Centro Sviluppo Materiali SpA) | Bufalini, A. (Centro Sviluppo Materiali SpA) | Lucci, A. (Centro Sviluppo Materiali SpA) | Scoppio, L. (Pipe Team srl)