A.N. Krasnov

Improving data transfer efficiency in a gas field wireless telemetry system

Effective organisation of communication channels in autonomous information and measurement systems (AIMS) is a burning issue. It is particularly challenging for areas where, for a number of reasons (primarily unprofitability or immaturity of the wired infrastructure), telecommunications can rely only on wireless technologies, i.e., radio channels. Arctic regions of the Russian Federation, where most of Russia’s gas and gas condensate deposits are located, constitute a typical example of such areas. The key challenges during construction of wireless communication channels are associated with the fixed range of frequencies that can be used without a licence. For the purposes of radio traffic, the frequency used by AIMS transmitters and receivers depends on the frequency of the quartz crystal resonators used in such devices. The stability of this frequency determines both the number of radio channels that can be used and the efficiency of data transfer. Key factors affecting the quartz frequency include temperature and “ageing” of quartz crystals. Known methods for increasing the frequency stability generally allow compensation for the temperature drift of the quartz frequency. In addition, such methods are increasingly energy-consuming, which is unacceptable in the Extreme North. This article suggests using GPS receiver data for frequency adjustment. With a minor increase in energy consumption, this technique enables full compensation for quartz crystal resonator frequency drift, no matter what the cause of such drift, eventually allowing operation of more radio channels within the authorised bandwidth with preserved channel separation. In general, it helps increase the efficiency of data transfer in the telemetry systems of gas field operations.

Cognitive model-based system of optimal control of methanol supply to the flowline

The main problem during natural gas extraction is the hydrating risk. Hydrates could be formed at every exctraction stage: from gas foundation to the Central Processing Facility (CPF). The operation conditions could hardly ever be performed without hydrates because these conditions depend on many factors. Hydrating is quite an undesirable process because it decreases the field operations efficiency and causes accidents. The process operating procedure of any production field provides some measures to prevent hydrating. Mostly, hydrate growth inhibitors are supplied to the gas flow, for example, methanol. At this time the most important problem is evaluation for the current conditions optimal methanol flow rate or the water-methanol solution concentration. The system of optimal control of methanol supply to the gas flowline is offered in the article. It is based on real time analysis of head temperature and pressure, temperature and pressure in the entrance of the CPF and the ambient temperature. At this case current parameters and their dynamic are analyzed. The hydrating conditions are diagnosed with the algorithm offered in this article. The hydrate conditions are diagnosed with the algorithm offered in the article. This algorithm includes the results of temperature and pressure dynamic analysis and the cognitive model based on expert knowledge. This system was tested in the Yamburg gas condensate field. These tests confirmed real methanol saving.

System of automatic hydrate growth inhibitor supply to the gas field flowline

In the framework of reservoir engineering it is necessary to consider that hydrates could occur on every stage of gas producing, gas conditioning and gas transportation. This problem is very important, especially for wells and flowlines of the high north foundations. Operation conditions without gas hydrate formation could be provided by different ways. The most common way is the hydrate growth inhibitor injection to the gas flow. The most useful inhibitors are methanol or the water-methanol solution. This inhibitor is injected by special devices (systems). The main problem of such systems is addressless inhibitor injection, thats why, inhibitor consumption increases whereas the gas-hydration control efficiency decreases. Some protecting points are selected in the gas flowline in the offered system of the automatic hydrate growth inhibitor feed. At these points there is the highest probability of gas hydrate formation. The temperature and pressure sensors the inhibitor proportioning device are located at these points. This device consists of the operated valve, the back-pressure valve and the regulating disk, and it is connected to the methanol accumulator bottle by the methanol pipeline. During gas hydrate formation the pressure difference occurs, and this pressure difference is radioed to the operator station. Further, the dangerous section is detected and the control signal is sent to the regulating reducing gear train. So, methanol is fed to the dangerous section where gas hydrate formation was detected. The offered system use allows one to optimize the inhibitors flow, to increase reliability of any gas field exploitation even without a full electricity supply system.

The automatic diagnostic system of gas well flooding

There is a problem of diagnosis of the gas-well flooding in the article. Flooding weakens development of gas fields. Thus, creating real-time system of diagnosis of gas field is actual and has an important scientific and practical meaning. The known diagnosis methods are very labor consuming, expensive and do not guarantee real-time diagnosis. The offered system of automatic diagnosis of flooding include mathematical treatment with special algorithms using every day results of wellhead temperature and pressure measuring. A mean square deviation is calculated for a central system unit and compared with a typical value measured under normal operating conditions. These operations are made with a period defined at telemetry systems setup. As a result, the system fixes availability or unavailability of flooding according to special criteria and forms a signal. This system was probed on some wells of Urengoy gas-field; and its effectiveness was proved.