Measurements of tight rocks

About Us The University of Manchester is at the forefront of shale gas research One of the first UK universities to begin researching shale in the modern era Associated with the Rock Deformation Laboratory, University of Manchester Over 40 years experience in the field of rock deformation More than 5 years experience in the measurement of shale properties, including fracture development and permeability to gas

Previously considered as seal rocks above unconventional reservoirs Emphasis has shifted towards an understanding of porosity, permeability and storativity Measuring transport properties under stress in tight rocks is often challenging but essential to understanding fluid flow It is important to take into account the effects of permeability reduction due to pore pressure drawdown during production from a gas well Shales/Tight Sands Modelling the performance of a reservoir from exploration well testing without taking pressure sensitivity into account will lead to an overestimation of well production rates and estimated gas in place

Tests can be performed in multiple orientations, usually parallel to bedding/foliation and normal to bedding/foliation. Reo Tight Rocks offers a bespoke service to suit your individual needs. Stress-Dependent Permeability Pore pressure oscillating method Pulse transient method Geomechanical Testing Elastic properties Unconfined compressive strength Confined compression/extension to failure Brazilian disc test Direct shear measurements Ultrasonic Testing Acoustic velocity Acoustic anisotopy analysis Additional Services Specimen characterisation Core photography Microstructural analysis Grain density Bulk density Loss on ignition (LOI) Sample Preparation - plug drilling, powder samples Reservoir modelling Commercial Services

Stress-Dependent Permeability Methods of permeability determination must take into account sensitivity to variation in confining and pore pressures A common generic law can be applied to all shales – written in the form: K = Aexp(-γ(Pc-αPp)) Different shales exhibit very different pressure sensitivities Varying pore pressure has a LARGER effect on k than varying Pc. Hence α > 1

Physical Explanation of Alpha If α > 1: pore pressure is fully effective so produces the same effect on permeability as the same change in confining pressure. If one thinks of a cylindrical pore with a stiff outer pore wall and an elastically softer inner pore wall, the gas in the pore compresses the inner wall (increases its diameter) more than the same outside pressure distorts the outer pore wall (shrinks its diameter). Effective pore widths are differently affected by changes in confining pressure and pore pressure. If α > 1: pores may be lined with an elastically softer phase than the grain supported framework of stiffer grains that transmits the outside-applied confining pressure to the pore spaces. Permeability to gas shows similar sensitivities to both confining pressure and pore pressure. α>1α<1

Mechanical Tests Understanding geomechanical properties, and how these vary with polyaxial stress states, is of growing importance to effective development of shale/tight sand reservoirs, and CO 2 capture and storage of waste disposal. With five different testing machines in our rock deformation laboratory we study aspects of these properties for a range of shales and related rock types, relating mechanical response to the rock microstructure. Normal to foliation Parallel to foliation 15 mm

Apparatus PERMEABILITY / ACOUSTIC VELOCITY Hydrostatic apparatus 1: this standard hydrostatic apparatus is provided with several sample assemblies adapted to measure both permeability and acoustic velocity (Vp and Vs). Argon gas is normally used as a pore fluid but other fluids may also be used. A synthetic ester is the confining pressure fluid. Confining pressures of up to 400 MPa are used (equivalent to 15 km depth of burial). The apparatus is operated at ambient temperature conditions. Porosity changes (elastic and inelastic compaction) can be monitored via a pore volumometer as total confining pressure is applied. PERMEABILITY AT ELEVATED TEMPERATURES Hydrostatic apparatus 2: this apparatus is dedicated to measuring permeability of tight rocks. Confining pressures of up to 60 MPa (equivalent to 2.6 km depth of burial) are generated by a water confining medium. Argon gas is presently used as a gas pore fluid. The apparatus is also equipped with a furnace that can reach temperatures of 200 o C.

Apparatus PERMEABILITY / GEOMECHANICAL Triaxial apparatus 1: this apparatus has been specifically designed for work on shale. Confining and pore pressure ranges are MPa. The furnace is capable of reaching temperatures up to 150 oC. Pore pressure can be gas or liquid. Samples up to 3 cm in diameter can be accommodated. A range of loading paths are available including; axisymmetric compression, axisymmetric extension, controlled normal stress, controlled mean pressure, etc. Simultaneous permeability, acoustic emission (AE) and acoustic velocity measurements can be made. Electrical conductivity can also be measured. Porosity changes (elastic and inelastic compaction) can be monitored via a pore volumometer as total confining pressure and/or axial load is applied. PERMEABILITY / GEOMECHANICAL Triaxial apparatus 2: this apparatus is able to apply axial differential stress via a servo-controlled system at confining pressure up to 400 MPa (equivalent to 15 km depth of burial). Argon gas is normally used as a pore fluid but other fluids may also be used. A synthetic ester is the confining pressure fluid. Controlled pore pressure and pore volumometry are available using either gases or liquids as pore fluids. Samples can be strained in both extension and compression at room temperature. Porosity changes can be monitored via a pore volumometer as total confining pressure and/or axial load is applied.

Apparatus GEOMECHANICAL Paterson gas apparatus: this apparatus operates in compression, extension and torsion at confining pressures up to 300 MPa. It uses argon gas as the confining pressure fluid to enable high temperature operation. It has the capacity to operate at very high temperatures (up to 1200 o C). Argon gas is used as a pore fluid. SHEAR / RESIDUAL STRENGTH TESTS ELE direct shear apparatus: the specimen is subjected to a constant normal load while an increasing horizontal (shear) force is applied to one of the sections of the shear box. The loading cell has a normal load capacity up to 3 MPa. Main Features: Reversible stepping motor for residual strength tests Infinitely variable speed drive from to mm min -1 Maximum shear force N or 5000 N using a 10:1 lever ratio device Speed drive ratio - stepper motor 1/ resolution

Apparatus UNCONFINED COMPRESSIVE STRENGTH / ELASTIC PROPERTIES The loading frame can exert up to 230 kN of axial load. Strain gauges can measure both axial and lateral deformation of the sample. Acoustic emissions can be recorded through 8 channels and Vp/Vs can be recorded. Unconfined compressive strength and both static and dynamic elastic properties can be determined. SAMPLE PREPARATION The sample preparation laboratory is fully equipped with: Core drill Horizontal wire saw Faceters trim saw Lapping machines Core end grinding machines Crushing and grinding machines for powder sample preparation

People Prof Ernest Rutter Dr Julian Mecklenburgh Dr Rochelle Taylor Dr Kate Brodie Prof Kevin Taylor Telephone: +44 (0)