Fatigue Life Analysis of Coiled Tubing in Deep Well Jet Plugging Removal

The coiled tubing plugging has become the main means of plugging in gas Wells in Xinjiang. These Wells are deep and have high pressure, which can easily affect the fatigue life of the operating coiled tubing. In order to improve the life of coiled tubing in high-pressure gas Wells, this paper studies the plugging conditions of coiled tubing in high-pressure ultra-deep Wells. Firstly, the cross section deformation of coiled tubing under high internal pressure is analyzed. Secondly, the factors influencing the fatigue life of coiled tubing and the influence of surface damage on the fatigue life of coiled tubing were studied. Finally, the mechanism of furrow damage caused by coiled tubing and the main measures to reduce furrow damage are analyzed. The following suggestions are made to improve the life of coiled tubing: select the right material and the right size coiled tubing;Use appropriate measures to prevent premature coiled tubing failure and reduce operating costs.

Mechanism analysis and process optimization of sand and plug removal with rotating jet in horizontal well

In the view of the problems existing in horizontal well,such as sand depositing and cleaning difficulty of borehole,a technology with rotating jet suitable to resolution of the problems was presented.Based on liquid solid two-phase flow theory,the analyses on the sand movement law and the swirling field influential factors were conducted.Results show that:1) With the increasing of displacement in horizontal section annulus,swirling field strength increases,and when the displacement is constant,the closer from the nozzle,the stronger the swirling field strength is;2) Head rotating speed and liquid viscosity have little influence on the swirling field strength,but the sand-carrying rate of fluid can increase by increasing liquid viscosity in a certain range;3) Rotating the string and reducing its eccentricity in annulus are conducive for sand migration in the annulus;4) The sand can be suspended and accelerated again and the swirling field strength is enhanced by the helix agitator.Hence,the research results provide the theoretical basis for the design and application of rotating jet tool.

Research on compound plugging removal technology and its application in Xinmu oilfield of Jilin

Most fault-block reservoirs in Xinmu oilfield belong to heterogeneous sandstone in characters which has low permeability, and reservoir pollution is a common phenomenon in this area. Acidizing deplugging in oil wells has become one of the major measures to improve production efficiency in the field. A compound deplug- ging technology in high efficiency low corrosion is developed for this kind of low permeability sandstone reser- voir. On the basis of profoundly understanding of the reservoir＇s physical properties and sensitivity, along with comprehensive analysis of the cause for jams in oil wells, a series of experiments are carried out in order to in- vestigate the dissolution reaction among samples and deplugging inhibitor, sample dissolving speed, formation fluid compatibility, reduction of secondary pollution, etc. Considered reservoir condition in nearby wells the op- timized compositional deplugging liquid formula is selected for this reservoir. It is featured by reducing the de- plugging reaction speed, extending solution for processing radius, preventing secondary damage in dissolution processing, and removing plug pollution effectively. To implement this high efficiency low corrosion deplugging measure based on reservoir condition in the borehole and nearby wells, a relatively better result of deplugging and production increasing is achieved, which enriches the measures to increase production in Xinmu oilfield, and this method can be applied to other similar oiffields for the purpose of maintaining the crude oil production and providing assistant for increasing the production significantly.