Summary The reproductive biology of the glossiphoniid leech Helobdella stagnalis in Utah Lake, Utah was studied for an 18‐month period from June 1970 to December 1971. In this lake it was found that the overwintering adult leeches produce two broods of young in May and June. Evidence is presented to support the idea that the same individual can produce two broods. Two complete cycles of gametogenesis also take place. Continuous water temperatures were recorded at the study site to correlate with reproductive activity. Gametogenesis appears to be temperature dependent with the first generation of sperm taking 4 months to be produced in the fall and winter months while the second generation of sperm is produced in 6 weeks during the spring. Egg production follows a similar pattem.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFor a number of years, the exploration and production industry has sought to prove the feasibility of monobore expandable liner extensions as an advantageous alternative to conventional casing designs. Included as part of the initial casing design, the goal of an expandable monobore liner extension is to enable the operator to drill deeper exploration and production wells with larger hole sizes at the reservoir. As a contingency plan, the goal is to enable the operator to isolate zones that contain reactive shales, sub-salt environments, low fracture gradient formations or other drilling situations without having to reduce the casing and subsequent drilled hole size into the reservoir. A one-trip, top-down expansion system was developed and tested to prove the feasibility of the expandable monobore liner extension concept, including the ability to provide an optimized, cost-effective casing configuration without reducing drilled hole size. During the development process, the need for expandable open-hole packers or optional cementation of the liner was identified and addressed. This paper details the development process for the expandable monobore liner extension system, including testing and the resulting commercial field deployment in an operator well to qualify the technology. This paper will demonstrate the challenges faced during various planning and execution stages and explain how those challenges were met, specifically in the following areas:• Pre-planning wellbore design options and considerations • Monobore liner extension selection, one-trip system reliability • System qualification • Zonal isolation requirements • Field installation considerations • Expansion process • Safety and environmental impact • Post deployment results
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