Thermometry

Geophysical researches at the control of mining of deposits essentially differ from the geophysical operations made in bored uncased boreholes. It is caused by that at the control various categories of wells are investigated at various modes of their operation, various technologies of researches are used and, at last, is frequent each cased borehole as the object of measurements, demands, an individual approach both to a technique, and to interpretation of the received data. Whereas at research of uncased boreholes and interpretation of results of their research typical gauges, standards more often are used.

Today, when the real situation in branch is that, that drilling volumes fall, the importance of the geophysical control over mining of deposits for a decrease of rates of falling of extraction and its subsequent stabilisation essentially increases.

In the control over mining evolve three basic directions: analysis of process of a development of reserves of deposits of oil, an estimation of efficiency of application of various methods of increase of factor of petroextraction, diagnostics of a condition of oil layers and wells.

The greatest volume of researches in production is carried out for the problem solving, the layers connected with diagnostics and wells.

Problems of diagnostics of oil layers and wells.

In a direction of diagnostics of a condition of oil layers and wells evolve three groups of problems.

1. Definition of production characteristics of a productive seam.
   • Definition of intervals of a stream and liquid absorption;
   • Definition of places of inflow of oil, water and gas;
   • Definition of efficiency of a seam and the fluid expense;
   • Definition of power parametres of a seam.
2. The control of a technical condition of well.
   • Definition of places of failure of tightness of a casing and borehole bottom;
   • Revealing interstratal annulus crossflows in well;
   • Research of intervals of punching of casing wells.
3. The control over operation pumping - a bont.
   • Definition of static and dynamic fluid level and petrowatershed in outside of tubes
   • Definition of a site and duty of deep pumps
   • Definition of tightness of pump-compressor pipes (PCP)
   • Definition of places of position and operation mandrels.

The geophysical methods applied to diagnostics of wells and layers.

Diagnostics problems dare at the positioned and unsteady duties of well. Generally diagnostics of wells and layers is carried out by methods of thermometry, a flowmeter survey, (soil) water content measurements, resistive metres, dence metres, barometries and noisemeters. Experience shows, that the most informative method at diagnostics problem solving is the thermometry. However, the thermometry (in comparison with other geophysical methods) is also the most difficult (in the methodical plan) a method.

Thermometry. Excretion working (giving and taking over) layers; revealing annulus crossflows from below and from above; revealing of intracolumned crossflows between seams; definition of places not tightness of a casing, PCP and borehole bottom; definition oil - gaseous - inflows of water; revealing of flooded layers; definition of dynamic fluid level and nefte - a watershed in outside of tubes; the control of operation and a site of the deep pump; site definition mandrels and bottom PCP; an estimation of a rate of flow in well; the control over column punching, the control over a seam fluid fracturing.

Features of thermometry at problem solving

Diagnostics

Key parametre which is measured and bears information loading in a thermometry method, the temperature is. The temperature is a power parametre of system and consequently any change of system owing to change of a duty of well, or increases in pressure, washing, failure of integrity of a column, etc. result ins abatements to temperature change (temperature distribution) in well. The system well-seam in this respect is very sensitive system since in practice thermometers with high resolution of the instrument are used.

Diagnostics is carried out during all "life" of well: at injection, operation and repair. Thus wells subdivide on types (categories) according to a duty, an operation method, a construction etc. From the point of view of methodical features of problem solving of well it is possible to assort as follows: standing idle, operating, mastered.

Diagnostics of wells during the various periods of "life" (injection, operation, repair) has the features. They are reduced to that problem solution is carried out at various duties of wells and, hence, at the positioned, quasistationary, unsteady and transitive temperature profiles in wells.

The thermal field is inertial: for disbandment of thermal perturbation in well time defined by thermal properties of system, duration of perturbation and applied instrumentation is required. Therefore the following feature is connected by that (at measurements) during the various periods of "life" of well on thermograms the thermal history of well can be reflected. So, at development after drilling the thermal anomalies connected with drilling, cementing, by punching etc. can be observed; under repair the anomalies caused by operation can be observed.

Problems are necessary for solving in a long time working wells at quickly varying processes connected with short duration of operation of well, and in a long time standing idle wells. Therefore, at mining of a technique of researches it is necessary to consider the feature connected with the time factor.

The technology of development taken over at the enterprises is connected with compressor application. By a call of inflow of a fluid the compressor creates live pressure in well. Here it is possible to evolve a mode connected with reprisal, and then, after air outbreak, a mode with depression on a seam, i.e. a combination of modes of forcing and selection. For development in well preliminarily tap off PCP through which it is possible to carry out researches. Necessity of problem solving for the intervals overlaped PCP, arises in injection holes of willows wells an electroimpeller pump.

Change of pressure in system can be observed not only at development, but also in a long time working wells. Differences can be in speeds (rates) of change of pressure that it is necessary to consider. In operating wells pressure and system change as a whole is observed at their short-term stop, and then at start-up. At scouring of excessive pressure (discharge) in outside of tubes before research of pumping wells there is rather fast change of pressure in system.

Development is characterised by short-term start-up of well. As a rule, the well before development is washed out, and more often, the fresh or freshened water. In such conditions if from a mastered seam salt water enters more, in a sump of wells there are conditions for occurrence of a gravitational convection. Besides, washing, depending on its duration, itself breaks a thermal field in well.

A number of deposits is characterised by high value of saturation pressure of oil gas. It result ins to that at well operation work with bottom-hole pressures below saturation pressure. In such conditions in well polyphase flows (oil, gas, water) are observed. At development of wells polyphase flows can, obviously, to arise and at more low pressures of saturation as the bottom-hole pressure here is defined by depth of descent PCP and can be even more low.

Distinction of formation pressures at simultaneously uncovered several objects, a high watering of wells at low production rates - is conditions which also are necessary for considering at temperature diagnostics as they can be reflected in a thermal field of well.

One more feature which should be considered at thermal researches, is connected with response rate of the thermometer. In case of high-viscosity oil, a dirt on hole walls, deposit presence in a sump response rate of the device can vary essentially, that, in turn, strongly deforms a temperature pattern. On the other hand response rate defines speed of registration. In any case it is limited. At quickly varying transients in well final speed of registration of temperature as can result in to distortion of registered thermograms.

Thus, there is a variety of the factors influencing distribution of temperature in well. For authentic problem solving it is important to know these factors and features of their display in concrete situations.

The main effects causing a temperature profile in a seam and in well, are: effect Joule-Thomson, adiabatic, barothermic, blendings and warmth of a degassing. Solution of practical problems bases on the analysis of the form of the temperature curve and sizes of temperature anomaly. Last (anomaly), in turn, precipitates out on the basis of comparison of the registered thermogram to geothermal (basic). Character of change of the form of size and a sign on temperature anomaly in time is defined as by comparison of the thermograms registered during the various moments of time (or at various duties of well).