Absircrci -Nowadays the importance of intrusion detection is amplified due to incredible increase in number of attacks on the networks. The ubiquity of the Internet and the easy perpetration of the attacks will lead to more hostile trafic on the Internet. With the advent of high-speed Internet connections, the organizations today find it dificult to detect intrusions. So multi sensor Intrusion Detection Systems are inevitable. The optimum distribution of traflic to the sensors is a challenging task. I n this paper we present a mechanism to split trafic to different intrusion detection sensors to make the task manageable. This splitting of trafic to each sensor is managed by policies enforced on the splitter by the management console. The system is adaptive in the sense that it can adjust the splitting policies for keeping load disparity among sensors reduced. This mechanism of policy-reloading also take into the account the similarity between all possible pairs of policies and tries to minimize the packet duplication rate during the operation of the system. Our mechanism is based on the observation that minimizing the percentage of traftic being duplicated can enhance system performance. We have also discussed the effects of reloading of splitting policies on packet duplication rate and load on sensors.
Formation testers are being widely used worldwide in open hole, especially in exploratory wells where fluid identification, downhole sampling, determining pressure and mobilities are very critical. Sometimes, due to tight formations, unconsolidated sands or excessive borehole washouts/breakouts, it is not advisable to pump, because with longer stationary times there is high risk of differential sticking. In this scenario, cased-hole formation tester comes into play. The whole operation involves perforating 1 foot interval in casing, then isolating the perforated interval with straddle packers (3.28 ft or 1m apart). This is followed by pumping to establish fluid type and representative sampling. Later, extended buildup is acquired for reservoir characterization until transient reaches the radial flow regime (Mini-DST). Well A is located in XYZ Block, Pakistan and is operated by Pakistan Petroleum Limited (PPL).Pressures and mobilities were obtained with wireline formation testing probe module across open-hole which found the formation to be ultra-tight. Pumpout could not be acquired with probe module due to formation tightness, therefore the question of fluid type was unanswered. Additionally, across the prospective zone washouts were observed. Due to these factors, the well was cased to establish fluid type and reservoir characterization (permeability, skin and pressure) through cased-hole dual packer formation tester. After 10 hours of pumping, first gas breakthrough was observed on downhole fluid analyzer. Pumping was carried out for almost 22 hours in order to get representative samples. This was the longest pumping time ever on any well in Pakistan. Later, buildup was acquired since hydrocarbon presence was established (Mini-DST). Cased-hole formation testing is very helpful when dealing with layered reservoirs as testing of each individual layer on a full-fledge DST operation would be very costly, especially if the layers end up being declared as water bearing. Similarly, conventional DST operation for ultra-tight formations can cost a lot of rig days, whereas mini-drillstem testing can conclude the same with reasonable amount of rig time. The most important benefit of cased-hole formation testing is its capability to pump for longer durations with no risk of differential sticking, thereby expanding the possibilities for formation testing and sampling.
Hydraulic or zonal isolation behind pipe plays a vital role in the life of a well. It guarantees well control, production from hydrocarbon zones and preventing the production of unwanted fluids. Perforation zone's selection and remedial jobs are based on cement integrity. Common challenges faced in cementing wells in Pakistan are presence of thief zones, water/gas invasion in cement and improper mud displacement resulting in cement channelling.Cement evaluation is as crucial as the cementing job itself. It is done using conventional sonic tools (CBL-VDL) which provides information about cement integrity. Sonic tools provide a qualitative uni-directional measurement. Then we have ultrasonic technology which measures "Acoustic Impedance" (AI) of annulus material; gives 100% azimuthal coverage with much better vertical and radial resolution than sonic tools. However, for light cements; the above conventional cement evaluation techniques cannot be used due to its limitations like:i) Effect of liquid and gas micro-annuli and dual casing ii) Inability to resolve micro-debonded/contaminated class G cement due to its threshold principle iii) Low acoustic impedance contrast between liquid and cement i.e. for liquid 1.4-2.6 MRayls and for light cement 1.5-3.6MRaylsTo address the above limitations a novel measurement of "Flexural Attenuation" (FA) is combined with AI that classifies the annulus material into three distinct states Solid, Liquid and Gas (SLG). In flexure mode casing is vibrated at an angle and combined with AI (vibration in thickness mode); giving us a unique output of SLG map. AI stand alone cannot evaluate light cements and contaminated class G cements with certainty.A case study is presented; where light cement slurry was used. FA and AI measurements technology was combined to evaluate for zonal isolation. First time in Pakistan an ICE "Integrated Cement Evaluation" processing was applied; specifically designed for light cements and confident answers were obtained successfully. The AI showed 40-50% liquid contamination whereas SLG map confirmed solidified light cement behind pipe. FA and AI together confirmed zonal isolation and in turn provided aid for successful well control and completion of the well.
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