The American Petroleum Institute (API) crush tests for proppants found in recommended practices (e.g. RP 56, 58, & 60) are typically used to compare the crush resistance of recognized API proppant sizes at a predetermined stress under dry and ambient conditions (API, 1995). This procedure has remained the same through several API committees since the early 1980swithout change. More recently, the International Organization for Standardization, ISO 13503–2, reviewed the procedure and made only slight changes, most notably in the time for which the stress is to be applied (ISO, 2006). The "new" procedure from ISO gives no indication of how the stress changes the overall mesh distribution. It also sheds no light on how key factors such as moisture, temperature, time, or cyclic loading change performance characteristics. This work addresses these issues. The down-hole environment where the proppants are placed is wet, hot, and pressurized. Incorporating these variables into a modified API test procedure for crush resistance better represents actual down-hole conditions to which a proppant is subjected. This information is critical in establishing required propped fracture conductivity, and thus, proppant selection. In this study a standard API crush cell was modified for pressurized fluid flow at temperature and used to quantify the effects of the parameters described as compared to standard API crush tests. Tests were performed on the following proppants: light weight ceramic (LWC), intermediate density ceramic (IDC), and high strength bauxite(HSB). Modified testing exposes critical proppant failures under conditions that more closely simulate those experienced downhole; these failures are not be revealed by current standard API/ISO test procedures. The modified procedure results in an improved method for better understanding downhole proppant pack performance. Introduction Proppant behavior and propped fracture conductivity have been studied in the laboratory since the earliest days of fracturing in the late 1940s (Gidley, 1989). Since that time a variety of mechanisms have been examined that are extrinsic (e.g. non-Darcy flow, cyclic loading, gel damage, etc.) and intrinsic (Krumbein shape factors, mineral content, acid solubility, etc.) to proppant performance in the fracture. However, extrinsic influences are not included in API or ISO industry standards for evaluating proppant crush resistance as this test is only a quality control procedure. Differences in performance and durability from one proppant to another can be the result of manufacturing factors including raw material mineralogy. Including extrinsic factors in testing can help to differentiate proppant performance under conditions that more closely reflect those downhole (Colt, 1995). Extrinsic factors, such as temperature, time, and cyclic loading and their effect on fracture flow capacity have been examined extensively in previous literature. Yet, this paper makes the effort to incorporate these factors synergistically into standardized crush testing for proppants. Liquid saturation of man-made proppants under pressure with exposure to these extrinsic factors enables one to differentiate proppants in a more relevant environment. This in turn will influence proppant selection and classification (Freeman, 2006 & 2008).

Nitrogen alone has demonstrated success as a fracturing fluid in reservoirs normally found sensitive to liquid systems. It has proved useful in shales of the Ohio Valley and West Virginia areas, and in similar lithology of the Fort Worth basin located in north central Texas. The fracture efficiency of nitrogen, as related to leakoff and flow capacity testing with no propping agent, has been investigated to analyze the effectiveness of nitrogen stimulation. Also, field data are presented that demonstrate successful results of the nitrogen technique in both oil and gas reservoirs. From the laboratory studies and field results, several conclusions were drawn concerning nitrogen stimulation. Of primary interest is that most of the width reduction in an unpropped fracture will occur in the early stage of production, which indicates a sharp decline of the well flow rate after a relatively short period.

Oil base muds (OBM) and their formulation can have a pronounced impact on cement performance in wellbores. This occurs when cement and OBM become mixed during normal well cementing operations. Increased mud contamination can ultimately compromise cement integrity. To minimize these mixing effects, the ability to improve compatibility of the mud system becomes paramount to completion success. The OBM base oil and the type and concentration of emulsifier can be especially crucial. The most common type of OBM primary emulsifier is a fatty acid which reacts with calcium hydroxide to form a calcium soap. A partially water soluble emulsifier (an alkanolamide) is used as a secondary emulsifier in most OBMs because it keeps the emulsion stable even if the calcium source is depleted, but it is rarely used as a primary emulsifier. When employed as a primary emulsifier, the alkanolamide has shown the ability to reduce the effects of OBM contamination on cement. In a correlative work similar benefits have also been realized by mixing a water soluble surfactant with cement. Proper design and management of an OBM system provides better cement performance. Although using an alkanolamide as the primary emulsifier costs slightly more than using a fatty acid, reducing the impact of OBM/cement contamination can more than offset the increased cost. Introduction OBM is used in drilling critical or difficult wells. OBM provides certain advantages such as borehole stability, temperature stability, resistance to contamination, lubricity, and superior penetration rates in certain formations. Oil muds are a water-in-oil emulsion consisting of three phases. The internal phase exists as water droplets emulsified within the external oil phase. This emulsion, sometimes called an "invert emulsion", is maintained by surfactants or emulsifiers to remain stable under downhole conditions. The third phase consists of drilled solids and commercial additives used to maintain required drilling properties. The solids phase is usually water wet, but the addition of surfactants which promote oil wetting help keep the solids adequately oil wet and in the external phase. Although the emulsion provides some properties of viscosity, suspension, and filtrate control, most drilling situations require augmenting these properties. P. 329^

Qualifying proppant performance prior to a frac job, or simply verifying proppant performance after a frac job, can add significant value to propped fracture stimulations. Through a blend of established practices and new technology, data can be generated that will give an engineer insight into how specific proppants are designed to perform. This is without running expensive and time consuming conductivity and permeability tests on every job. A primary objective is to establish representative, reliable and reproducible data via a sample collected from a large mass. American Petroleum Institute (API) Recommended Practices (RP) identifies three primary tenets:representative sampling from a flowing stream,standardized testing with calibrated equipment, andsample retention for follow-up evaluation. Application of these practices ensures that proppant test data is valid (e.g. representative, reliable, and reproducible). Yet, these practices alone typically quantify quality but do not qualify proppant performance.1, 2, 3 Correlation of valid well-site proppant data with published information (literature, web-sites, or fracturing simulators) enables one to identify disparities. Any differences in part may be the result of mining anomalies, manufacturing defects, transportation abuse, and/or contamination. These can directly impact the delivered performance of your chosen proppant. Since proppant flow capacity or conductivity is a key measure of that performance, some empirical results have been assimilated for well-site and public data. As a consumer, having information that describes the proppant at the well-site is important to deciding application and value. By compiling historical well-site proppant data one can set a minimum threshold of required properties or specification. This provides the opportunity to identify a greater range of proppants (e.g. substitutions) that meet reservoir, economic, and supply chain needs. Lastly, this paper introduces new patent-pending technology that enables well-site proppant sampling and evaluation before the fracturing treatment. Having pre-frac data gives one the opportunity to make any necessary changes in fracture design and implementation to get the most from available proppant. It also provides for a detailed inspection of the well-site delivered proppant supply. For instance, one can isolate and sample each pneumatic trailer, monitor associated pneumatic discharge pressures, provide representative split samples for fracturing fluid compatibility testing, etc. Case histories, onshore and offshore, support "qualifying proppant performance". Introduction As stated in previous literature4, proppant conductivity or performance is very important in the design of propped fracture stimulation treatments. It is equally important that the designed performance arrive at the well-site to protect your investment. How does one ensure that occurs? Current quality control practices, which are often static and cursory, do not provide the scientific basis to evaluate quality, let alone performance. This is because those methods, which do not follow API recommended practices, are not subscribed to by the supply chain as a way to obtain representative, reliable, and reproducible data. All too often, static or scooped samples are extracted for measurement. As a result, the entire proppant mass has not been sampled and has not been evaluated. This paper demonstrates how to apply quality control practices in order to evaluate, promote, and qualify proppant performance at the well-site. Doing so will provide the best opportunity to match designed and delivered propped fracture performance expectations.

W s pgper focuses cm the use of a delayed Recent developmrktsin foamed fluids have inproved cross-lfnkfng mechanl sm uhfch has proven to eniranee critical foam properties: viscosity, flufd loss fracturingsuccess cm several formstf ons within the control,and proppant transport. North Texas, East Texas, Oklahorm,and Bakersfield, Califomfa areas. Laboratoryresults indicate the One of the most crttical character stics of any foamingof a delayed cross-lfnking gel increases fracturingfluid is its viscosity. Modification of apparent viscosities,as well as sand transport and this property can greatly affeet overa11 foam fluid loss propertf es bey(md those of foamed linear performance. Thus, polymers have been added to the gels. Iiquid phase of foa~to inprove apparent viscosity in the fracture.l S Polymers also have other A detai led explanatlcmof a i ,100 foct ,,,,,~.-----.. h~A I'lweqllre advantages (fluid loss control and proppant single pass pipe viscometerand fluid loss apparatus transport enhancenmt ). For instance, is provided. cii rrent. Results suggest foam cross-lfnkedgels follow pwer law flufd behavf or, possessing 44% nftrogen puwing and vaporizingpractices have al1 but necessf tated that proppants,chefffi cals,T;~. ,hh igher viscositiesthan conventi onal foams. Fluid added to the 1fquid phase of foams. loss testing also shcms a 40% reduction in leakoff beycnd ccmventi onal foams. Dynamic proppant support nesultedin concentratedslurries at the surface. for foams is not perfect according to parallel plate Pneumsti c transfer of proppants into a fluid on the PUW's dlscharge side has been practiced in s observati ak.Fall rates for conventional foams 9"5 areas, but renminsin the developnsntal stages. * uhf1e affected by foem quality are two orders of Therefore, in additicm to improving foam nsi~itude greater than foam cross-linked fluids. Resultfng proppant profi1es are believed to be performsnce,the addition of natural or synthetic polymers facilftates the transfer of surface super-l or to conventional foams due to virtually concentratedslurrf es uhfch cofmnonly reach 16 ppg infinfte statf c proppant support.proppant cafcentrati ons. More than 100 treatmentshave been completedusing a Attew@s were made at foam?ng er~$~-linkedgels soon delayed cross-linking foam.A revisw of local formationcharacter stics and treatment ccmditfaks after their introductionto the fndustrywith little success,indieating that surface cross-linkedborate are discussed regarding the success of a and titanate gels were apparently too viscous and cross-linkedversus conventionallfnear gel foam.unyieldingfor adequate foam generation. Yet the recent advent of delayed cross-linkedgels, whether tfm or temperatureactivated, has permitted foam INTRODUCTION generatim of lfnear gels at surfacewhile providing the downhole properties of a foamed cross-linked During the past 20 years, numerous technical papers gel. and articles have been wrftten on the subject of foam fracturing. From the foaming of a variety of In additfon to testing methods used, this p...