The evaluation of the effect of fracture geometry on permeability based on laboratory study and numerical modelling

The geometry of fractures includes orientation, spacing, aperture are among the parameters affecting permeability in rocks. Studying the effect of fractures geometry on the permeability in a laboratory scale requires the selection of a suitable sample in terms of physical and mechanical properties. Therefore, in this study, fibrous fiber was selected due to low water absorption and permeability as well as its non-brittle behavior and flexibility. In order to investigate the effect of fracture geometry on the permeability, 1, 2, 3, and 4 fractures with spacing greater than 50 mm, 50 mm, 25 mm, and 15 mm and with orientations of 0, 15, 30, 45, and 60 degrees to the horizon in the sample were created. The fractures did not come into contact with the surface of the sample .The results showed that the permeability raises exponentially with increasing orientation and decreasing the spacing. This situation is mostly seen in fractures with orientations larger than 30 degrees. Also, the permeability measured in the laboratory was compared with the results obtained from the numerical method of distinct elements and UDEC software. The results showed an error of about 10-15%, which is well-matched between the permeability obtained from the laboratory and the numerical method.

TIBIAL DIAPHYSEAL FRACTURES;

Objectives: To evaluate the management of tibial diaphyseal fractures treated byPOP cast versus intramedullary nailing in terms of time of union. Design of study: Randomizedcontrolled trials. Setting: Department of Orthopaedic, Allied / DHQ Hospital, Faisalabad.Duration of Study: Six months (01-08-2013 to 31-01-2014). Materials and Methods: 80patients fulfilling the inclusion and exclusion criteria were included in the study. After laboratoryand radiological assessment, the patients in Group 1 were treated by long leg cast. The patientsin Group 2 were treated with intramedullary interlocking nail. The patients were followed on OPDbasis. Results: 80 patients divided into 2 groups. Each group had 40 patients. Mean age ofpatients was 30.99 ±8.092 years. There were total of 65% males and 35% females in this study.According to geometry of fractures simple transverse fractures were 47.5%, spiral fractureswere 17.5%, oblique fractures were 25% and segmental fractures were 10%. There were 71.25%closed fracture and 28.75% type l open fractures. Mean time of union was 23.86 ± 5.48 weeks ingroup 1 while in group 2, mean time of union was 18.35 ± 4.12 weeks. P-value was 0.001 whichis statistically significant. Conclusion: It is concluded that reamed intramedullary interlockingnailing is a good mode of internal fixation comparing with conservative management of closereduction and POP cast in both close and type I open fractures in terms of union.

Predicting permeability and gas production of hydraulically fractured tight sands from microseismic data

The main objective of hydraulic well stimulation is creating fractures in a tight rock that enhance its natural permeability and make hydrocarbon production economic. Because the geometry of fractures and the permeability of treated formation influence the subsequent production, their assessment is important for the development of tight-gas fields. The fracture shapes and orientations are inferred conventionally from microseismic data acquired in the process of well stimulation, but the same data also can be used to estimate the formation permeability. We have compared two techniques for permeability estimation that utilize different aspects of information contained in the observed microseismicity. We applied those techniques to data recorded in the course of the hydraulic fracturing of four wells drilled in the Pinedale Field, Wyoming, U.S.A. Then we used the obtained permeabilities to predict the gas rates from 20 treatment stages at which the number of identified microseismic events was sufficient to perform our analysis. The predictions of both techniques correlate with production and allow us to establish the characteristics of rocks and hydraulic fractures that make good producers at Pinedale.