Stability of production section in south Iraq
The drilling of the production section in the development wells in South Iraq could face numerous problems related to the partial or total losses, flow of sulphurous water, significant change in pore pressure along the wellbore, tight hole and caving among others. One of the main issues observed in several fields across South Iraq during well construction is the stability of in the production section of wellbore (especially in the shale formations). The instability of the open hole led to time consuming incidents related to an inability to run open hole logs to the wells total depth. Additional time has also been spent on wiper trips, reaming and backreaming, and on incidents related to hole pack off and stuck pipe. To solve the problem several steps were taken starting with the creation of a mechanical earth model which identified the main problematic formations presented by shale and the possible root causes of instability. This involved core characterization analysis including X-ray diffraction, cation exchange capacity and thin section analysis were performed to identify the structure of the shale. In addition the fracture development tests were performed on the samples of core and from this the main root causes of instability were identified. Based on the theoretical research and the laboratory tests new drilling fluid formulation together with best drilling practices were proposed that would allow the elimination of the problem due to the stability of the wellbore in the shale formations.
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core test; drilling fluid; graphite; microfracture; shale; stability; washout; wellbore; графит; кавернообразование; керн; микротрещина; раствор; скважина; сланцевые породы; стабильность DOI 10.17122/ogbus-2013-6-58-80 References to this article (GOST) A.G. Ruzhnikov. Stability of production section in south Iraq // Electronic scientific journal "Oil and Gas Business". 2013. №6. P.58-80. URL: http://ogbus.ru/eng/authors/RuzhnikovAG/RuzhnikovAG_1.pdf