This paper discusses a real case study on how formation damage can be removed after finishing all operations in drilling and completing a well that is used vertically for producing commercial hydrocarbons using Over Balanced Drilling (OBD) techniques. Formation damage happens in every drilled well during field operations. It is an undesirable and complicated situation usually caused by solids invasion, fines movements, organic precipitation and deposition, and collapse and swelling formations (clay formations). The production performance of drilled well is significantly affected by the scale of damage in the invaded formation of the pay zone.

No abstract

No abstract

Oil and gas well drilling planning is the main task of any drilling engineer. In order to overcome this task, it is required to maintain the wellbore pressure between the maximum value that does not fracture the formation and the pressure of the fluids within the formations, because, as the wellbore pressure exceeds the fractures' pressure, formation damage occurs, which will consequently result in lost circulation problems. Meanwhile, if the well pressure is less than the formation fluids pressure it leads to other drilling problems such as the kick problem and possibly blowout. The maximum well pressure that does not fracture the formations is called the fracture pressure and the formation fluids pressure is called the pore pressure. Therefore, pore pressure and fracture pressure are considered as the most crucial parameters for drilling engineering planning and for launching new wells. Another significant parameter for well planning is the detection and estimation of an abnormal pressure depth. This is when the formation pressure is higher than the normal pressure at a specific depth.There are many methods for determining pore pressure, fracture pressure and abnormal pressure depth and their values. These methods can be divided into two categories: predictive methods and verification methods.In this paper, the predictive method involves determining or estimating the above-mentioned parameters prior to drilling operation using seismic data, especially equivalent to matrix stress. This is applied to two case studies: an African sandstone reservoir in Libya and the South Texas Frio Trend, based on seismic data recorded for interval transit times vs. depth. The results showed that; first, for the African sandstone reservoir, Libya, the oil filed the abnormal pore pressure located deeper than 6000ft, which is the main indicator for specifying that the maximum depth has an abnormal pressure. Second, for the South Texas Frio Trend, the abnormal pore pressure was located at deeper than 8000ft. In the last section, based on the pore and fractured gradient, the casing sets are selected.

Lost circulation refers to loss of part of or whole drilling fluid into the formation while drilling operataion. It wastes costly mud and wastes time spent on rig operations. In this study, the investigation of a natural plant called, Prosopis Farcta (PF), has been done to show its effectiveness as a natural lost control material. A series of experimental tests have been conducted in order to discover the effectiveness of the PF as an LCM. Moreover, different particle sizes of the PF have been tested to find out the optimum size. Furthermore, a variety of PF concentrations have been tested in order to investigate the effect of the LCM percentage. And finally, for the purpose of comparison, a similar particle sizes and LCM precents of the most used conventional LCM, calcium carbonate have been tested as well. The results show that the filtrate rate of the reference mud (without additives) was 32 milliliters in 30 minutes. The most achieved reduction in the fluid losses with the addition of CaCO3 LCM was about 47% and this was by adding 20 ppb of the fine sized CaCO3 into the reference mud. Whereases, 76% reduction in filtrate was obtained by adding only 15 ppb of the fine sized PF.