Research On Hole Cleaning Of Extended Reach Well&Highly Deviated Well

The situation of oilfield in domestic suggests that the most oilfield have already entered the later period, and most are "hard to use" resource, conventional wells can not meet the needs of the reality. With the improvement of drilling technology, all kinds of wells with complicated structure, such as directional wells, horizontal wells, extended reach well arises at the historic moment and on the increase. It provides powerful conditions for the speeding up of the development of the oil industry. But at the same time, new problems emerge in endlessly. Because of the large deviation angle and horizontal displacement, this kind of well, especially highly deviated well and extended reach well, has large horizontal displacement and long inclined well section. Under the force of their own gravity, cuttings deposit in the ring easily and form a layer of "cutting bed". Pump suffocation, sticking and other accidents may easily occur if the well was not cleaned enough, the effect of hole cleaning has direct impact on drilling efficiency, drilling cost, wellbore quality, drilling safety and so on.Practice proves that the hole cleaning must give full attention, or the consequences which mentioned earlier will appear. It may influence the drilling effect seriously so that the operation in the well drilling process cannot proceed. It is one key to the complicated structure well. The key technology of hole cleaning is to build prediction model, some experimental research and theoretical research has been carried out and some achievements has been made. It provides some guidance for qualitative evaluation and application in the field. However, because of the complexity of the question, the comprehensive and reliable model has not formed yet, so the research on the hole cleaning still need a lot.Based on the above, This paper first through a large number of access to domestic and foreign relevant materials, so various existing simulation experiment results and theoretical research results can be known by the classification and organization of the data. The hole cleaning technology condition can be introduced in detail in accordance with the timeline of technology development.Next, the cuttings transport in the highly deviated well is always difficult to the technology researchers, so this paper is established in practicality. The entire borehole is divided into several paragraphs according to different deviation angle, which is based on different deviation angle with different cuttings transport mechanism and different requirements for hole cleaning, then the cuttings transport mechanism of each interval is expounded respectively. Because in drilling process of the highly deviated and horizontal section, the unstable cuttings bed can be formed easily. So this paper focuses on these sections and analyzes the forces of cuttings, and further analyzes the all kinds of cuttings transport forms. At the same time, the typical flow models in the annulus are introduced in this paper.And then, hole cleaning, which combines theory and technology, has become the key to the drilling of highly deviated well. The process of cutting is very complex, due to a number of factors, which including fluid annular velocity, hole inclination and hole geometric features etc, can affect the cuttings transport. These factors are correlated and constrained each other. In order to establish the mathematical model of hole cleaning, it is necessary to understand the factors of cuttings transport. This paper reorganized the main factors and described the key factors in detail for comprehensive and profound understanding.After that, hole cleaning mathematical model can be built respectively. Many scholars at home and abroad devote themselves to study highly deviated well and extended reach well for years. They did lots of experimental and theoretical research on the hole cleaning to explore the mechanism of the cuttings transport and establish the corresponding mathematical model. Given that the existing models is difficult to be utilized in practical engineering application because of too many parameters or variables, the complicated relationship and different influences which factors effects cuttings transport. Based on the existing models, this paper absorbs and uses for reference the outstanding achievements of the classical mode, whose shortcoming have been modified and complemented. In addition, this paper focuses on the introduction of the highly deviated and horizontal section.Finally, in order to assist the field engineers to predict the hole cleaning situation more accurately and help to fix the hydraulic parameters or drilling operation parameters, the corresponding application software is developed according to the built model. Using object-oriented programming, the hole cleaning application software of highly deviated well is developed whose integrated development environment is Visual Basic6.0and database management system is Microsoft Excel as a result, the aim to guide the practical engineering application is achieved.