A new well testing response from lateral cross flow within layers is described. The response occurs when there is extremely low effective vertical permeability in the system at the larger scale. Low vertical permeability actually accentuates the layering and reduces vertical cross flow whilst enhancing lateral cross flow from within-layer heterogeneities. The response is investigated using numerical simulation of flow in end-member models of complex and geologically realistic architecture in high net-to-gross fluvial systems. This ‘ramp’ response is shown to form one member of a family of well test pressure transient responses. The other members of the family include previously-described negative geoskin and geochoke. The use of well test data to characterize these particular types of layered fluvial reservoirs is an important step in the static-dynamic integration of geological and reservoir engineering models.
Most recent history shows that polytetrafluoroethylene (PTFE) is widely used as antifrictional materials in industry for wide speed range. A high antifriction property of PTFE makes it suitable for dry friction bearing. Main disadvantage of using PTFE is its high wear rate, so extensive research had been carried out to improve the wear resistance with addition of filler material. This study focuses on four input parameters load, sliding speed, sliding distance, and percentage of glass fiber as a filler material. Taguchi method was used for experimentation; each parameter is having 3 levels with L27 orthogonal array. Grey relational analysis is used to convert multiple response parameters, namely, wear and coefficient of friction, into single grey relation grade. The optimal input parameters were selected based on the S/N ratio. It was observed that load 3 kg, sliding speed 5.1836 m/s (900 rpm), sliding distance 2 km, and 15% of glass fiber are optimal input parameters for PTFE without significantly affecting the wear rate and coefficient of friction.
We applied a recently introduced method to complete a feasibility assessment and design a stress testing campaign in a deep-water field in West Africa. We first reviewed the previous—and unsuccessful—campaign. Test data were inverted together with a priori knowledge from an independent geomechanical study to develop an understanding of the ambient conditions. Based on this understanding, the current campaign's chance of success (COS) was estimated to be 10%, with 1,000 psi of pressure capacity lacking to reach 95%. By analyzing the sensitivity of the risk to formation properties and design parameters, we identified various options to prevent this high, yet seemingly controllable, risk of test failure. Among them, a 1.7-ppg increase of mud density, expected to increase the COS to 80%, was deemed most effective and implemented. With 4 successful tests out of 10, the second campaign was more successful than the previous one. Yet this success rate was lower than anticipated. We inverted the second campaign's test data to revise our understanding of the in situ conditions. Our main findings are that, for this particular case, (i) the magnitude of the minimum horizontal stress was significantly higher than initially thought, (ii) the minimum horizontal stress and the horizontal stress ratio appeared to be anticorrelated, and (iii) the COS was extremely sensitive to the minimum horizontal stress. The conditions solved using the second campaign's dataset also explained the first campaign's negative outcome. This case study demonstrates that (i) the proposed planning method enables return of experience to be captured and leveraged from one test, or one series of tests, to the next, and the design of formation stress tests to be optimized, leading to an improved success rate of formation stress tests; and (ii) the proposed inversion scheme allows insight to be gained from both successful and unsuccessful tests, including in formation conditions other than the minimum horizontal stress.
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