TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractRestimulation of existing wells represents a vast underexploited resource. A successful refracturing treatment is one that creates a fracture having higher fracture conductivity and/or penetrating an area of higher pore pressure than the previous fracture. Refracturing requirements are different in highly permeable formations (high fracture conductivity) as compared to low permeable ones (moderate fracture conductivity). Understanding these basic differences is essential to a successful restimulation.
A model is developed to characterize wireline formation tester sticking from quantitative analyses of the most prevalent sticking modes. An appropriate description of differential pressure sticking mechanics for stationary logging tools and cables forms the foundation of the model, and a supplemental formulation provides a quantitative relationship for key-seat development based on borehole and tool parameters. The results of the analysis are converted into a sticking probability formula that allows quantitative risk assessment at the job planning stage. The primary form of the model uses mud cake parameters derived from a wellsite evaluation device, but an alternative formulation utilizes laboratory and field measurements of mudcake properties and only requires conventionally available parameters for risk assessment. The model is calibrated and tested by application to a database of 664 formation testing jobs in the Gulf Coast area. The resulting strong correlation between calculated sticking probability and actual fishing frequency illustrates the power of a model-based approach to risk assessment. In contrast to most statistically based approaches, it is possible to incorporate a large number of relevant parameters and quantitatively examine risk levels as adjustments are made. Direct measurement of mudcake properties at the wellsite will further enhance the risk assessment accuracy. P. 79
Environmental concerns in Pennsylvania related to Marcellus Shale development are high. One of the issues to which the Pennsylvania Department of Environmental Protection (PADEP) has given a high priority is the threat of methane migration into fresh water as a result of methane leaking to surface from behind casing. This has become a significant problem for Marcellus operators as leaking annuli on both new and existing wells is not uncommon. This paper outlines the steps that Flatirons Development took to demonstrate to PADEP that the annular leaks on a recently drilled and cased Marcellus lateral posed no credible threat to ground water and that completion of the well should be allowed to proceed. In early June, 2011, Flatirons became aware of bubbling in the water filled cellar of the DU 3-6-1H. This discovery came just as completion operations were set to begin. Subsequent investigation revealed that there were two leaks, one from the production-intermediate annulus and another very small leak from the intermediate-surface annulus. PADEP issued Flatirons a Notice of Violation (NOV) and requested that fracture treating the well not proceed until the issue had been resolved. Over the following two months, Flatirons implemented a series of diagnostic procedures meant to assess the short and long term environmental threat, determine the cause of the problem, trace the source of the gas, and, if necessary, formulate effective remediation options. Using a variety of tools including ultrasonic imaging, pressure build-ups, noise-temperature logs, gas isotopic analysis, cement sample analysis, and continuous monitoring of annular flow, Flatirons was able to demonstrate that the fresh water aquifer was not threatened by methane migration. This work was presented to PADEP's Gas Well Integrity study group and helped form a basis for revising regulations governing leaking annuli.
This paper reviews the design and implementation of four enhanced recovery projects that were initiated in the shallow-water environment of two bay fields located along the coastline of South Louis; ana. These four projects are a caustic augmented waterflood, a miscible carbon dioxide waterflood, both in Quarantine Bay Field, and two polymer augmented waterfloods in the West Bay Field. The paper focuses on the design modifications required for the projects due to the hostile overwater environment and the logistics problems associated with the locations'of the projects.
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