Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage (MFL) inspection, liquid ultrasonic inspection, electromagnetic acoustic transducer (EMAT) inspection and remote field eddy current (RFDC) inspection for oil and gas pipeline girth weld defects. Additionally, it introduces the new technologies for composite ultrasonic, laser ultrasonic, and magnetostriction inspection, and provides reference for development and application of oil and gas pipeline girth weld defect in-line inspection technology.

In this study a hybrid finite element-statistical energy analysis (FE-SEA) method is used to investigate the structure-borne noise of a steel-concrete composite railway bridge. The rail is represented by an infinite Timoshenko beam connected to the sleepers which are regarded as finite Timoshenko beams supported in ballast.The fasteners and ballast are simplified as a series of springs with complex stiffness. This model allows the receptance of the track to be determined. The wheel-rail forces are computed in the frequency domain from the contact-filtered roughness and the receptances of the wheel, track, and contact. The forces transmitted to the bridge are determined by substituting the wheel-rail forces into the equation of motion for the track. This model could also be applied to a slab track mounted on a bridge. A hybrid FE-SEA method is introduced in which FE is used to model the concrete deck and SEA is used to model the steel girders. This enables the computation of the vibration and noise of the composite railway bridge. The proposed method is verified by comparing its predictions with field measurements. The structure-borne noise level of the bridge is found to increase with train speed v by approximately 20lg(v). It is shown that the adjacent spans in a multi-span bridge can be ignored in deriving the bridge-borne noise at receiver points in the middle of the main span, provided that the distance to the track centreline is less than 0.3 times the length of the main span.

No abstract

The analysis results of long-distance oil and gas pipeline failures are important for the industry and can be the basis of risk analysis, integrity assessment, and management improvement for pipeline operators. Through analysis and comparison of the statistical results of the United States, Europe, the UK, and PetroChina in pipeline failure frequencies, causes, consequences, similarities, and differences of pipeline management, focusing points and management effectiveness are given. Suggestions on long-distance pipeline safety technology and management in China are proposed.

No abstract

No abstract

No abstract

Water-alternating gas (WAG) displacement is a pronounced technique to improve gas or/and water injection in heterogeneous reservoirs. For the last half century it has been successfully applied to more than 60 oilfields worldwide. However, its mechanism still deserves further investigation. In this work, a series of water, gas, and WAG displacement studies were conducted with a sets of glass micro-models which were reproduced from a target reservoir rock by copying the pore structure images into the glass media. The pore size and geometry structure of the glass micro-model are very similar to the original. The proceeding of WAG displacement was video tape recorded versus time so that the kinetic saturation to each phase in the porous media can be obtained though a PC based image analyzer. Corroborated with the measured pressure drop across the model, the effect of WAG on mobility control is systematically studied. The results show that the mechanism of WAG flow in porous media is much different from two phase (gas-oil and water-oil) flow. For water displacing oil, a piston-like displacement mainly occurred in the small pores (assisted with capillary pressure) and a non piston-like displacement mainly occurred in large pores. For gas displacing oil, the piston-like displacement occurred in both large and small pores as long as the viscous forces can overcome the capillary force. In general, the piston-like displacement gives a higher displacement efficiency than non piston-like displacement. Channeling of displacing phase (water or gas) caused by heterogeneous feature of the pore media was observed. However, when three phase (water-gas-oil) flow is involved, the mechanism of displacement is changed. The oil phase becomes intermediate wetting, and the gas becomes non-wetting phase and water phase remains a wetting phase. Water phase prefer to occupying the small pores due to capillary effect, while the gas prefer to occupying the large pores. The oil phase presents in the porous media in a discontinuous status; the feature of oil flow is mainly in the form of oil slug or oil film at the interfaces between water and gas phases. Accumulation and expansion of gas phase from the large pores expel the oil phase into down stream. With the proceeding of WAG displacement, the oil slug becomes smaller and finally turns into oil film; the residual oil saturation in average after WAG displacement is less than 20% OOIP, benefited from a reduced size of oil drop. It is found that pore geometry has a significant effect on residual oil saturation. "Snap off" effect plays a very important role to cut off the oil slug into oil blobs and form gas bubbles during WAG displacement. Increase in cycles of WAG tends to reduce residual oil saturation. Oil blobs trapped in very tiny pores, pore corners, and dead pores are the main type of the residual oils. At the last, an optimal WAG project to the target reservoir will be presented. Introduction Many micro-tests indicate a phenomenon in almost all water-wet reservoirs developed with water injection[1]-[4], that the injected water flows quickly along a layer and forms serious fingering. This trend increases with the water wettability. Field production dynamics also confirm that along with water-driving development, water cuts are rising very soon, even flooded by water, although the recovered oil is not a great percentage of reserves in different types of reservoirs.