Weak signal detection is very important in the downhole acoustic telemetry system. This paper introduces the Duffing oscillator weak signal detection method for the downhole acoustic telemetry systems. First, by solving the Duffing equation, analyzed the dynamics characteristic of Duffing oscillator and weak signal detection principle; and then on this basis, built Duffing oscillator circuit ba...

Reliable and sufficient welltest data is necessary for the evaluation of reservoir properties and well performance. Best results a r e usually obtained by monitoring downhole pressure and flow rate continuously during a transient test. However, a recurring problem for geothermal welltests has been the failure of the downhole pressure instrument in the high temperatures and hostile environments,...

A modelling effort was made to try to predict the life of downhole tubes or casings, synthetically considering the effect of service influencing factors on corrosion rate. Based on the discussed corrosion mechanism and corrosion processes of downhole tubes, a mathematic model was established. For downhole tubes, the influencing factors are environmental parameters and stress, which vary with se...

At present, mud pulse transmission systems are widely used in downhole data transmission. But the systems are very low in transmission efficiency, only 5 10 bits/s, with very large anti-inter-symbol-interference (ISI). It cannot meet high requirements for high-speed transmission of modern logging system. The development of communication technology has laid some foundation for this requirement. ...

Week 6 of Expedition 356 (Indonesian Throughflow) consisted of completing operations at Site U1462 (including another successful downhole logging deployment in Hole U1462C) and the start of operations at Site U1463 (proposed site NWS-2A). The science party was able to finalize all outstanding reports from Site U1461, particularly downhole logging and stratigraphic correlation, and begin finaliz...

The recently developed smart well technology allows for sectionalized production control by means of downhole inflow control valves and monitoring devices. We consider borehole radars as permanently installed downhole sensors to monitor fluid evolution in reservoirs, and it provides the possibility to support a proactive control for smart well production. To investigate the potential of borehol...

Downhole microseismics has gained in popularity in recent years as a way to characterize hydraulic fracturing sources and to estimate in-situ stress state. Conventional approaches only utilize part of the information contained in the microseismic waveforms such as the P/S amplitude ratio and/or P first motion polarity to determine the microearthquake focal mechanisms and infer stress state. Thu...

In this paper we develop and demonstrate a method to estimate the reservoir pressure and a productivity index for vertical steam wells, from its production characteristic (also called output) curves. In addition, the method allows to estimate the radius of influence of the well, provided that a value of the reservoir transmisivity is available. The basic structure of the present method is: firs...

Increased production from gas lifted oil wells can be achieved by use of feedback control. Without control the well system may have large oscillations in the flow rate or stabilize itself at a non-optimal production point. These non-optimal production conditions give lower production and/or poor oil/water downstream separation. The study extends the newly introduced approach for controlling gas...

Seven hundred and nineteen samples from throughout the Cainozoic section in CRP-3 were analysed by a Malvern Mastersizer laser particle analyser, in order to derive a stratigraphic distribution of grain-size parameters downhole. Entropy analysis of these data (using the method of Woolfe & Michibayashi, 1995) allowed recognition of four groups of samples, each group characterised by a distinctiv...