Laboratory measurement of low permeability unconventional gas reservoir rocks: A review of experimental methods

Transient pulse test and morphological analysis of single rock fractures

A modified pressure-pulse decay method for determining permeabilities of tight reservoir cores

Gas permeability evolution of clayey rocks in process of compressive creep test

An improved method for permeability estimation of the bioclastic limestone reservoir based on NMR data.

The Boda Claystone Formation (BCF), explored as a possible geological disposal of HLW in Hungary, has peculiar physical and chemical characteristics. Due to the petrophysical behaviour many new methods and experimental development were applied, while the traditional methods, e.g. steady state flow test on the basis of Darcy’s law, are too time-consuming. The pressure pulse decay (PPD) technique destinated to estimating gas and water permeability is one of these new methods developed for the BCF study. The main advantage of the PPD permeability compared with traditional permeability measurements is that very fast (in case of kg ∼ 10−19 m2 15–25 min, kw ∼ 10−21 m2 6–7 h), only 0.1–0.5 MPa pressure difference applied in the two sides of the examined core, quasi in situ circumstances can be provided and their uncertainty estimated. For the correct interpretation of results of the three cores originated from different underground boreholes of the formerly URL’s Alpha-1 drift, geochemical, minerological and petrophysical analysis were carried out. The time-consumption of drying, the fact that the dry core absorbed humidity of the atmosphere very fast, as well as the unsuccess of saturation under vacuum drew attention to the importance of the necessity of careful preparation and handling as well as the necessity of geochemical and mineralogical analysis.

Laboratory pressure pulse decay permeability measurement of Boda Claystone, Mecsek Mts., SW Hungary

Statistical analysis of vitrinite reflectance data—a new approach

Abstract Proppant is one of the major elements of a hydraulic fracture process that can influence the productivity of an oil or gas well. The permeability of a propped fracture may be determined through laboratory measurements, utilizing experimental relationships, or using analytical methods. All methods have their advantages and disadvantages, and this study attempts to offers a solution that combines the various methods to achieve a practical solution. The standard measurement method for fracture conductivity and permeability is a time-consuming and delicate procedure and can be performed only at the cost of a significant degree of uncertainty. Investigating a method that can predict fracture permeability in significantly less time and with an acceptable level of accuracy would be useful for the industry. Proppant can be viewed as an unconsolidated, heterogeneous (in size distribution) although well-sorted granular packing, and the different relationships that can predict the permeability of such systems may be utilized. Such interdependencies account for the frictional pressure drop caused by the proppant particles and often neglect the pressure drop caused by the surface of the apparatus. To extend the applicability of the various models, the combination of a theoretical model that accounts for the pressure drop caused by the fracture wall with those models would have clear practical advantages. For this reason, a new equation had to be developed that establishes the relationship between the fracture permeability and the so-called modified particle friction factor. Since the frictional pressure drop correlations usually contain porosity as a parameter, determining its value under reservoir conditions is essential and a new procedure had to be developed. Since the different relationships were developed under different conditions to those under which the proppant-packs are usually used, providing a solution to the issues of their wide range of application is the primary objective of this study. 

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Semi-analytical approach to the determination of fracture permeability

The Upper Pannonian (UP) sandstone formation has been utilised for thermal water production in Hungary for several decades. Although sustainable utilisation requires the reinjection of cooled geothermal brine into the host rock, only a fraction of the used water is reinjected in the country. UP sandstone formation is reported to exhibit low injectivity, making reinjection challenging, and its petrophysical properties are poorly known, which increases uncertainty in designing operational parameters. The goal of the study is to provide experimental data and to gain a better understanding of formation characteristics that control injectivity and productivity issues in Upper Pannonian sandstone layers. Petrographical characterisation and petrophysical laboratory experiments are conducted on cores retrieved from two wells drilled in the framework of an R&D project at the depth of between 1750 m and 2000 m. The experiments, such as grain density, porosity, permeability, and ultrasonic velocity, as well as thin section, grain size distribution, XRD, and SEM analyses, are used to determine Petrophysical Rock Types (PRT) that share distinct hydraulic (flow zone indicator, FZI) and petrophysical characteristics. These are used to identify well intervals with lower potential for injectivity issues. The results imply that fines migration due to formation erosion is one of the key processes that must be better understood and controlled in order to mitigate injectivity issues at the study area. Future investigation should include numerical and experimental characterisation of formation damage, including water–rock interaction tests, critical flow velocity measurements, and fines migration analysis under reservoir conditions.

/pdf/experimental-rock-characterisation-of-upper-pannonian-2dvz6wea.pdf

F. Fedor

Papers

Laboratory pressure pulse decay permeability measurement of Boda Claystone, Mecsek Mts., SW Hungary

Statistical analysis of vitrinite reflectance data—a new approach

Semi-analytical approach to the determination of fracture permeability

Experimental Rock Characterisation of Upper Pannonian Sandstones from Szentes Geothermal Field, Hungary