Wang Ruihe

Continuous Measurement-While-Drilling Utilizing Strap-Down Multi-Model Surveying System

In the oil drilling process, measurement-while-drilling system is usually used to provide real-time monitoring of the position and orientation of the bottom hole. Usually the bottom drill string attitude is measured on the condition that the drill string is static. Particularly, in rotary steerable drilling application, it is a challenging problem to accurately measure the spatial attitude (inclination, azimuth, and tool face) of the bottom drilling tool with the drill string rotating. A set of “strap-down” measurement system was developed in this paper, the triaxial accelerometer and triaxial fluxgate were installed near the bit, and real-time well deviation and azimuth can been measured. Laboratory experiments show that the dynamic solver methods will meet the project requirements. However, according to the drilling field tests, playback analysis on storage data of the underground measurement indicates that drill string vibration is the main reason for measurement errors. So, by setting a time window, the real-time measurement of the accelerometer and the flux gate signal are processed and analyzed, the movement patterns of the rotary drilling tool at the bottom were judged within the time window. Stick-slip phenomenon is utilized to improve the measurement accuracy and to reduce the impact of lateral vibration of the drilling string on the measurement system. We could take advantage of stick-slip phenomenon because of it cannot be avoided completely, although it should be avoided in order to improve the drilling string operating life. Simulation results showed that recommended dynamic survey approach could effectively enhance measurement precision, and deduce effect of vibration on resolve results.

Experimental characterizations and modeling of electrical resistance in hydrate bearing sediments

Electrical resistance is an important method in characterization of oil/gas reservoirs, and can also be applied to gas hydrate bearing formations. Formation of gas hydrate has many significant impacts on subsea sediments. Since electric ions are excluded in hydrate, hydrate formation can change the distribution and mobility of electrolytes in subsea sediments, which will affect the resistance of the sand matrix. In this study, experiments have been conducted to measure resistance in a large sand pack simulating the conditions of hydrate formation in sub sea sediments. The resistance of the sand matrix with various hydrate saturations is measured, and the results are discussed based on the Archies formulas for rocks. The effect of gas hydrate is revealed. The data presented in this paper can be used for the characterizations of the porosity and hydrate saturation in hydrate bearing subsea sediments during well logging.

Development and evaluation of a new nanometer based spacer NMS-I

In view of the inadequate cementing quality in the cementation for long isolation intervals of oil and gas wells, and considering the field practice in Tarim Oilfield, a nanometer material LC-212 was introduced as the base stock to experimentally develop a new spacer system NMS-I, in combination with other materials, including a chemical gel plugging agent, carboxymethyl cellulose and barite. Experimental results indicated that the system had a wide adjustable range of density, good rheological property, static stability and compatibility with cement slurry. It also showed no flocculating or thickening effect on the water-base drilling fluid and low-density cement system. Meanwhile, the capacity of lost circulation control and the influence of the spacer on the second interfacial cementing strength were evaluated by a self-made lost circulation simulator and shearing test facility. The results showed that the spacer had favorable plugging and flushing effect, and the second interfacial cementing strength can be greatly improved. Moreover, based on the experiments, the mechanisms of spacer function were analyzed. The results obtained from the investigation offer a novel approach to resolving some practical problems in cementing jobs.