تأثیر تنش‌های ناشی از عملیات حفاری بر چاه و ضریب پوسته

Forces of drilling bit cause a lot of changes in rock characteristics, especially in rock mechanical properties. Changes of reservoir lithology cause pressure drop around wellbore during production procedure. Routine tests were carried out in all the wells after completion and unexpectedly high Darcy skins were estimated from the test data for all of the wells. In order to prepare prevention and remediation plans, it is crucial to understand the source of the skin. Determination of skin factor due to changes in drilling process (force and tension of drilling bit) around wellbore is very critical. The main purpose of determination of drilling bit effects is to control and prevent formation damage around wellbore. A lot of research has been performed regarding skin factor around wellbore. However, given the effects of drilling process such as stress on skin factor, attempt has been done to determine the effects of these parameters on skin factor around wellbore. The results of these analyses prove effective and controllable influence of drilling and skin factor around wellbore. The research shows controlling and reducing of skin factor around wellbore by appropriate planning of drilling and drilling bit. Another aim of this research is the explanation of the relation among different processes in petroleum industry to prevent formation damage. By careful examination of the structure before drilling planning and drilling bit selection, formation damage will reduce dramatically and destructive pressure drop in reservoir can also be prevented.