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.
The question of influence of a number of cycles of the threaded tool joint screwing – unscrewing on the coefficients of friction and as a consequence on the final value of the torque moment is considered in this article.
To study this question the tests were carried out in order to:
to identify the influence of a number of grip pings and torque moments on the final result of a torque moment at screwing a new nipple with a new clutch;
to identify the influence of a number of grip pings and torque moments on the final result of a torque moment on screwing a new nipple with the previously operated clutch.
The coefficients of friction for the tool joint thread in dependence on a number of screwing-unscrewing cycles and also in dependence on the clutch and nipple state were obtained empirically. On the basis of the obtained data, the dependence diagram of the friction coefficient of a number of cycles of screwing – unscrewing was plotted. As a result of this experiment the following information was obtained:
The threaded joint running for the threaded tool joint without a surface treatment using a lubricant is in increasing the coefficient of friction;
The difference in the coefficient of friction and a torque -dependent moment between the first cycle of screwing – unscrewing and the subsequent ones is considerable and as a result must be taken into account in the analysis of the spontaneous torque moment problem.
A number of cycles of screwing – unscrewing was obtained on which reaching the torque moment becomes equal to the one calculated theoretically and the further screwing operations don’t lead to the increasing the torque moment.
The comparative analysis of the sulfite liquor properties (technical lingosulfonatov), obtained by wood lignin sulfonation in relatively acidic and neutral environments, was conducted. During the research by electrochemical method there was obtained the dependence between redox potentials of lingosulfonatov solutions and pH value, and there was conducted the comparative analysis of redox potentials values depending on the method for producing sulfite liquor. There was significant distinction among liquor solutions conductivity values of different methods for producing. Differentiated determination of acidic functional groups of the structural units of lignosulfonate-fenipropanovogo link was conducted by the conductometric titration method, and there was the significant sulfogroups excess in the liquors obtained by the neutral sulphite method of wood lignin boiling. Moreover, the complexing ability of neutral sulphite and sulphite liquors for producing was researched by the potentiometric titration method. As a result, there were obtained potentiometric titration liquors solutions curves by salts of polyvalent cations (Fe II and Fe III). These studies have been allowed a comparative evaluation of reactivity and an opportunity of lingosulfonatov liquors polymeric matrix application as bases for producing of chemical reagents used in drilling technology. It was found that the drilling reagents on bases of liquors by the neutral and sulphite boiling method have several advantages since their obtaining base on the modification of lingosulfonatov matrix by less expensive reagents modifiers. The above mentioned studies in conjunction with relatively low cost, low foaming power and high resistance to high temperature were allowed to recommend the liquors of the neutral and sulphite boiling method as the perspective raw material for the drilling reagents production.
In the current drilling technology today pointed out the problems associated with the instability of work downhole drilling motors , they stop, short service life of working devices (WD) and accidents (lapels, destruction elements DDM) layout of the drill string (DS). In particular, the timing of the engines, depending on the size and operating conditions, ranging from 90 to 235 hours. Failures DDM according to drilling companies “Gazprom drilling” and “CSA Deutag» – from 5 to 12 per year; which leads to long-term recovery efforts in the well, or the complete elimination of the latter. From the practice of using found that about 50% of all failures associated with DDM wear working devices are a pair of friction rubber-metal (stainless steel rotor – rubbersteel-stator).
Solving complex scientific and engineering problems calls for a considerable amount of experimental research and testing in order to study and obtain an objective assessment of the impact of various factors on the change in the studied parameters. In this regard, we install II-5018 was reconstructed to study the tribological properties of the “elastomer – rinsing liquid – the metal” as applied to the interaction of the friction pair “stator – rotor” in the PDM. To this end, as close to reality friction pair “rubber – metal”. The article discusses the problem of choosing the methods of laboratory tests, which must meet the requirements and standards applicable standards and regulations to carry out standardized tribological tests and studies to determine the physical and mechanical properties of rubber.
The results of complex investigations in the field of studying the processes of friction and wear of friction pairs elastomer-metal with the purpose of improvement of a technique of study of tribological aspects of the power section of screw downhole motors.