Papers by Keyword: Wellbore Instability

Abstract: With the continuous production of the well development, sidewall instability phenomenon has become increasingly serious, mostly occurs in the shale formation, benefit for oilfield produced great harm. Water-based drilling fluid sidewall instability mechanism has been basically clear, the oil-base drilling fluid influence on sidewall stability is not yet concrete. So this paper mainly for oil-based drilling fluid hard brittle shale sidewall instability mechanism research. This article first from the perspective of chemistry, the hard brittle shale borehole wall instability is studied, the experiment tested respectively by the white oil and water treatment of hard brittle shale of cation exchange capacity (CEC) value, so as to analyze the same and the hydration of clay mineral equivalent after processing samples, through analysis of the temperature, time, media's impact on hard brittle shale wellbore stability. Secondly, from the Angle of mechanics, stress and mechanical properties of mud shale formation is analyzed, and the minimum drilling fluid density model, gives a variety of analysis and calculation formula. In addition, this paper adopted the X ray diffraction (XRD)

Abstract: It is accepted that the water flux in/out of the shale during drilling is the key factor, which controls wellbore instability. This flow can be divided into two components:1) the hydraulic flow due to the difference between the wellbore and pore hydraulic pressure; 2) the osmotic flow due to the imbalance between activities of the shale and the drilling fluid. The former can be prevented by adjusting the wellbore hydraulic pressure balance in the well hole, while the latter is much more difficult to control . The water activity of shale is a controlling factor in many areas of drilling. It impacts all situations wherein the temperature or the stress state of a shale is altered such as in wellbore stability, drilling rate and hydraulic fracturing. This chemical “potential activity interaction” produces a mechanical failure due to the movement of water in/out of shales. In order to have no shale alteration, it requires that the chemical potential of each component must be the same in all phases. This is seldom the case. After a lot of studies the shale activity is shown to be a function of pressure and temperature. Results showed inverse relationship between the platelet distance and the shale water activity. This experimental method proves to be a reliable and efficient way for studying the relationships for the shale water activity, comfining pressure, temperature, and platelet distance.

Abstract: This paper will take the complex layer of the Qunkuqiake region of Tarim Basin as a research object in order to find the reasons of the borehole instability. The layered drilling fluid design technique is put forward firstly and a new drilling fluid technology to solve the problems of wall instability of the Qunkuqiake regions in Tarim Basin is developed.

Abstract: In this paper, the conception of natural fracture stress in rocks is given according to mesomechanics analysis. The quantitative analysis about wellbore collapse and stratum fracture is made and the density range of drilling fluid is determined. The result is the same as the conclusion which was given by the traditional Mohr-Coulomb criterion in petroleum engineering. The new method of combining mesomechanics with fracture mechanics is used to study the wellbore stability in petroleum engineering, which can reveal the nature of the rock deformation mechanism and provide theoretical reference to design of the drilling engineering.