Abstract Over the last few years shale plays across North America have received significant attention because of their revenue potential and the supplementary reserves they add to the U.S. natural-gas reserves. However, the flow capacity (i.e., permeability) of these shales is very low and, therefore, requires some sort of stimulation to make them economically viable. Problems during stimulation treatments can lead to "pressure outs" and screenouts. One of the main reasons that lead to "pressure outs" is high process-zone stress (PZS). With high PZS, the chance for pressuring out is higher than screenout (i.e., one can still flush the job at lower rates provided the sand has not settled in the wellbore). The purpose of this work is to show the effects of high PZS in shale stimulation treatments and the associated production from such zones. Examples are presented from three shale wells in the Rocky Mountain region. Well A provides examples from the Gothic and Hovenweep shales, while Well B consists of an example from the Mancos shale. A Diagnostic Fracture-Injection Test (DFIT) was performed in the Gothic and Hovenweep shales before the stimulation treatment, and the results obtained point to very high PZS. History-match analysis of the Gothic and Upper or Main Hovenweep stimulation treatments using a grid-oriented, fully functional three-dimensional (3D) fracture simulator confirmed the same. Solutions are provided to overcome this effect and successfully "place" the stimulation treatment. However, the production associated with such high PZS zones is not very encouraging. Well A is temporarily abandoned because of poor production, and the Mancos shale well with high PZS (Well B) is one of the poor producers in the field. Finally, another example (Well C) from a successful Mancos test is also included in this work to show the difference in production between high- and low-PZS zones. This paper discusses methods for early identification of high-PZS shale zones to possibly avoid stimulation treatments in order to pay more attention to the low-PZS zones that require stimulation.

Abstract The precipitation and accumulation of scale deposits is a major concern for production companies in the Uinta Basin. Since 2003, conventional hydraulic fracturing treatments with scale inhibitor pumped simultaneously as an additive have been offered to this region. This service proved to be very effective in the Permian Basin using borate crosslinked fracturing treatments (with scale inhibitor concentrations as low as 5 gal/mgal). However, these design criteria and formulation of the scale treatments had to be changed significantly to be effective in the typical Uinta Basin gas well environment: low permeability (<0.1 md), multi-layered, commingled gas reservoirs. Typically, a well completed and placed on production without any scale inhibitor in the Uinta Basin may show signs of scale buildup in as little as 30 days. The effects of the scale accumulation can be seen everywhere from an exaggerated production decline to scale deposition on production equipment. This paper outlines the learning procedure and present designs, testing and monitoring results from scale treatments together with a case study from the Uinta Basin.