3890689051

Solid Stale Phenomena

ISSN: 1662-9779. Vd. 240. pp 94-97 doi:!0.4028/www.scientific.net/SSPJ40.94 & 2016 Trans Tech Puhlications, Switzeriand

Suhmitted: 2014-11-16 Revised: 2015-05-29 Accepted: 2015-04-15

Online: 2015-08-28

Development of Stand for Rock Materiał Fracturing in Laboratory Conditions

Piotr Kędzierski¹ a’, Tadeusz Niezgoda^1band Grzegorz Sławiński^1,6

¹ Military University of Technology, Kaliskiego Street 2, 00-908 Warsaw, Poland

^[e-mail], ^[e-mail], ^[e-mail]

'corresponding author

Keywords: Fracturing test stand, Rock tensile strength.

Abstract. The paper presents a dcscription of the stand for rock materiał fracturing in laboratory conditions. Rcquircmcnts to bc met by fracturing stands wcrc formulated. Propcr operation of the test stand was vcrificd by marblc spccimcn fracturing. Many of tcchnical dctaiLs of the devclopcd stand wcrc givcn, which may bc uscful for readers designing their own stands.

Introduction

Fracturing is a wcll-stimulation tcchniquc in which rock is fracturcd by a pressurized fluid. A fluid injcctcd into a wcllborc crcatcs cracks in the dccp rock formation in order to rclcasc unconvcntional deposits of hydrocarbons. The costs of drilling, the possibility of rccording and analyzing proccss parameters and obtaincd cracks make it advisablc to study the fracturing proccss in the laboratory. The application of a stand is cspccially bcncficial in the casc of comparativc studics of various fracturing fluids which dcmand the same test conditions. Ishida et. al [1J presented the test stand for rock fracturing with the usc of liquid and supcrcritical COą. They invcstigatcd cubic spccimcns (17cmxl7cmxl7cm) which wcrc placcd in a pressure celi to providc hydrostatic strcss conditions. The spccimcns had a 2 cm diameter central hole in which the packcr was inserted to injcct COą.

The aim of this paper is to providc dcscription of a stand for rock materia! fracturing. The developcd stand allows the tensile strength of rock to bc determined. Among methods for tensile tests on rocks, one wcll-known indircct method consists in comprcssing cylindrical spccimcas across their generators is Brazilian method [2]. Howcvcr, this method has significant limitations in terms of the fracturing proccss. Firstly, a spccimcn cannot bc cxamincd in a different strcss stale. Sccondly, an influence of various fracturing lluids on broakdown pressure cannot bc evaluatcd. The proposed test stand solvcs the abovc mentioned problcms. Additionally, during post proccssing, a fracturcd spccimcn may bc scanncd with the usc of computcr-assistcd tomography to assess the amount and distribution of cracks.

Requirements

The stand for fracturing should ensure conditions elose to thosc occurring in the fracturing of actual wcllborcs as far as possiblc. Depending on the depth, the rock mass is in a uniaxial strain State or in a geostatie State, which is charactcrizcd by cqual pressure in all dircctions. Thcreforc, a fracturing test stand should enablc rcscarchcrs to put a rock spccimcn under confming pressure. The application of the cxtcmal load is aLso drivcn by possibility of using fracturing lluids (c.g. liquid CO2) which occur in the cquilibrium State under the pressure greater than the tensile strength of the sclcctcd matcrials. Furthcrmorc, the stand should maintain the tested spccimcn at temperaturę prcvailing at a givcn depth, which rcsults from the geothcrmal gradient.

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