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At present time the interest to the quantitative interpretation of temperature surveys is growing. Individual flow rate and reservoir pressure of each layer, behind-casing flow rate, hydrodynamic layer parameters, characterization of permeability changing at near-wellbore zone become the purposes of quantitative interpretation. Non-stationary temperature and pressure in the well are used as input data for transient processes analysis, and temperature logs are used for quasi-stationary analysis. Particular interest is in determination of the individual layer flow rates and near-wellbore zone parameters.
The paper studies the problem of unsteady temperature field in heterogeneous reservoir during fluid filtration. The aim of this work was to develop and provide rationale for simplified analytical model of non-isothermal single-phase fluid filtration in heterogeneous reservoir. Analytical solution for the temperature field in the formation after flow rate changeis obtained by the method of characteristics. Two assumptions were made in solving the problem: radial thermal conduction and compressibility of saturated porous medium are ignored. Analytical models are compared with the numerical solution of the problem. Radial heat conduction and compressibility of oil- or water-saturated reservoirs influence insignificantly on the unsteady temperature field after the flow rate changes.
It is possible to solve the inverse problem on the evaluation of the damage zone radius of the permeability in the reservoir basing on the model curves of the temperature change after flow rate change. The possibility of that method realization is demonstrated on model curves of the temperature change.
APPLICATION OF SENSORS-SIGNALER SAND AND DRIP MOISTURE TO THE MONITORING MODE OF THE WELLS UNDERGROUND GAS STORAGE
The article shows the relevance of monitoring the removal of particulate matter and condensed moisture in the product UGS wells, gas and gas condensate fields. Comparative characteristics of used domestic and foreign acoustic control in the gas flow phases is given. Particular attention is paid to the simultaneous control of the content of sand and condensed moisture alarms sensors that do not require expensive verification schemes and allow reliable assessment of the dynamics of the processes at the wellhead and gas gathering points. The results of operation of the combined alarm sensor DSS-AKE-2 on the two largest domestic UGS. The necessity of a direct calibration of acoustic sensors on the technological objects of different configurations is set. It is shown that the currently used in advanced devices such as DSS-A modification and the production of “Sigma-Optic” in performance is not inferior to foreign analogues in the implementation of operational monitoring wells operating parameters. The devices allow a timely manner to prevent flooding, the formation of clay-sand plugs, as well as reduce the risks of abrasive destruction of gas production equipment. The analysis of existing designs of detectors and alarms sensors showed that the sensor performance DSP-AKE-2 is not inferior to any domestic or foreign analogues, and for the simultaneous control of sand and condensed moisture superior to them and may be subject to import substitution. They can be used to predict the destruction of the reservoir, the formation of clay-sand plugs, reduce erosion-corrosion wear of gas production equipment and to minimize the costs of cleaning and preparation to transport gas.
Insufficient ultra-deep drilling caused by many technical and technological challenges, but more complications at the drilling of deep horizons, which forecasts and warnings are not developed enough. The article examines the characteristics of complications at ultra-deep drilling (deeper than 6 km). Major complications during drilling ultra-deep wells are connected with the manifestation of abnormally high reservoir pressures (AHRP) and high temperatures. The most common complications such as curvature of the borehole and the resulting emergence of gutter workings, lost circulation, the instability of deep rocks that form the wall of the well, the loss of mobility of the drilling tool under the influence of differential pressure, i.e. the drill pipe clamps. While in the shallow and deep horizons there are similar kinds of complications in terms of the elimination of deep-seated deposits significantly complicated by the action of specific ultra-deep factors, such as high temperature, pressure and the stress state of rock. Synthesis and analysis of processes, complicating drilling at depths, allows to differentiate complications in two groups: the first group consists of the complications caused by only geological and geophysical features of the well section the second – the processes and phenomena that occur during drilling operations at depths. The conclusion about the need to develop research in the study of complications in ultradeep drilling, which will more actively pursue drilling to deep horizons in the oil and gas regions.
MATHEMATICAL SIMULATION OF LIQUID-GAS MIXTURE SEPARATION IN A WELL AFTER FORMATION FLUID FLOW SHUT-OFF
Shut-off of fluid recovery from one of formations at simultaneous selective-zone well operation leads to a natural process of liquid-gas mixture separation. Water holdup in a well after complete separation makes possible to estimate water cut of the blocked formation. This method has advantages over other techniques because provides acquisition of data on water cut for each formation individually, it is characterized by short-term effect because of fast liquid-gas mixture separation and by accuracy due to performance of measurements in close proximity to a formation. For this reason simulation of separation process in an interval from a suction pipe to borehole bottom becomes actual.
After fluid movement stop in “pump suction” interval one can consider process of coarser-grained oil-in-water emulsion separation. It follows that time of complete separation depends on disperse phase size (oil droplets or gas bubbles) and difference in water and oil density. That is why movement of oil and gas bubbles in relation to a fixed water column according to Stokes’ law is used as a movement model when simulating.
From simulation results the following characteristics of phase distribution in a borehole are determined by means of application program package “Matlab” (density, pressure, phase concentration in mixture). These characteristics show the following:
methods sensitive to changes in medium density are the most suitable for determination of phases interface limits;
in case of use of geophysical sensors for definition of phases interface limits with help of a model it is possible to calculate a required quantity of these sensors for estimation of water cut with prescribed accuracy
the model provides solution for various inverse problems connected with mixture separation in a well.
Parameters of unsteady movement of injected fluid in tubing string during operation of pulsing devices
During the operation of pulsing devices on the well face there are short-term overlappings of a through bore for liquid pass as a result of which water hammers appear in the column of injected liquid, the parameters of which depending on the difference of elasticity of liquid and the tubing are transferred to the last one. In this regard there is a need to define the analytical dependences characterizing the values of pressure and speed of movement of liquid in any arbitrary cross section of a liquid column inside the tubing. To study these processes a problem of distribution of a water hammer of viscous liquid in the tubing from operation of pulsing devices on the well face on the basis of N.E. Zhukovsky’s classical equation about a water hammer was solved. Linearized equations of unsteady liquid movement represent a linear hyperbolic system and are a special case of telegraph equations. The problem was solved by the variable separation method which consists in finding particular solutions of the considered system meeting the set conditions. Entry and boundary conditions taking into account the unit at the bottom end of the tubing of reformative pulsing devices are set, and the column is isolated by a packer. The common decision of non-uniform system, according to the known formulas, is decomposed in Fourier series. As a result, we obtained expressions for speed of propagation and pressure amplitudes of hydroblows of injected liquid from operation of pulsing devices in the tubing on the well face. The received expressions were analyzed resulting in regularity of determination of amplitude of hydroblow pressure change in any cross section of the tubing being revealed. It will allow to predict in advance the most dangerous sites from the point of view of long-life reliability of a column of pipes during cyclic liquid injection in the system of reservoir pressure maintenance.