Abdel-Alim H. El-Sayed

Resistance of Cemented Concentric Casing Strings Under Nonuniform Loading

This paper discusses the case of two opposing unidirectional collapse loads uniformly distributed along the diameter of a single casing string and two cemented concentric casing strings. The stress distribution in the casing and cement and the deformation of the pipe are determined by adapting known solutions in the mathematical theory of elasticity to the problem of single- and dual-casing strings subjected to this type of loading. Results were obtained for the case of uniform hydrostatic radial collapse loads for the two casing sizes (9 5/8 and 7 in.) and their cemented structures. The resistance of the single pipe to this type of nonuniform loading may drop to 11% of its design resistance to uniform hydrostatic collapse pressure. The resistance of the cemented concentric strings under uniform and nonuniform loads is about the sum of the steel pipe resistances under the same conditions. The paper also includes the superposition of uniform and nonuniform collapse loads and the practical implications of these results. The authors conclude that nonuniform loading should be considered in casing design, especially opposite salt formations.

Two New Chemical Components for Sand Consolidation Techniques

Sand production problems are encountered throughout the world and recently detected in Saudi Arabian oil fields. Therefore an increased emphasis is being placed on proper initial well completion as the value of non-renewable oil reserves increases and cost of remedial work skyrockets. Sand control by consolidation involves the process of injecting chemicals into the naturally unconsolidated formation to provide in situ grain-to-grain cementation. Techniques for accomplishing this successfully are perhaps the most sophisticated ones undertaken in completion work. Many methods have been suggested to consolidate the wall of the wellbore for few inches or feet around the hole. These methods are either expensive or temporarily. This paper introduces two new cheep chemical components to be used to consolidate friable sand formation at temperature up to 300oC. The paper introduces these two components, discusses the physical and petrochemical properties of the consolidated sand and the factors affecting this consolidation and highlight the laboratory process and field application of these two components. Introduction Sand production problems are experienced in many oil and gas productive formations [1]. They are most significant in unconsolidated sandstone reservoirs. Sand influx into the wellbore may lead to various problems such as erosion of valves and pipelines, plugging the production liner and sand accumulation in the separators. Cleaning and repair works related to sand production plus loss of revenue due to production rate restriction amounts to great costs incurred by the industry every year. Furthermore, undetected erosion of production equipment may pose a major safety hazard in case of high-pressure gas wells. Therefore, sand control has attracted much research effort for more than six decades [2]. Sand production is explained in several ways. The most convincing theory attributes sand production to friction and resultant pressure drop as well fluid passes through the small pores of the sand body. If the cementing materials are not strong enough and that the pressure drop is high, the individual sand grain is displaced and carried into the wellboe. Another plausible explanation considers the fact that the formation compaction as the bore pressure decreases, and the variations of the load, tends to shift sand grains and shear the cementing material. Another strong explanation highlights the chemical difference between the water initially present when the sand grains were first deposited and that water contained in the aquifer. Water production can actually dissolve a part of the cementing material between sand grains. SPE 68225 Two New Chemical Components for Sand Consolidation Techniques Abdel-Alim H. El-Sayed*, Musaed N. Al-Awad & Emad Al-Homadhi, King Saud University, Riyadh, Saudi Arabia,