Shehzad Ahmed

Erratum to: Experimental investigation of immiscible supercritical carbon dioxide foam rheology for improved oil recovery

The original version of this article unfortunately contained a mistake. The presentation of an author’s name was incorrect. The corrected one is given below.

Effect of polymer additives as foam stabilizer for CO2 foam flooding

T prolific Niger Delta basin is a mature petroleum province. Therefore, further prospectivity in the basin lies within deeper plays which are high pressure and high temperature (HPHT) targets. One of the main characteristics of the Niger Delta is its unique diachronous tripartite stratigraphy. Its gross onshore and shallow offshore lithostratigraphy consists of the deep-seated Akata Formation and is virtually exclusively shale, the petroliferous paralic Agbada Formation in which sand/shale proportion systematically increases upward and at the top, the Benin Formation composed almost exclusively of sand. This stratigraphic pattern is not exactly replicated in the deep offshore part of the delta. The downward increasing shale percentage in the older and deeper parts of the basin poses a great problem to drilling. Increasing shaliness usually leads to wellbore instability and such other problems as pack-offs and stuck pipe. These hazards are the main causes of non-productive time in expensive deep-water or high temperature and high pressure (HPHT) drilling operations. Moreover clay mineral diagenesis generates mixed layer clays at higher temperatures and this tends to cause overpressures that may lead to disastrous kicks, losses and even blowouts. Predicting and managing drilling in such over-pressured or problem sections will form a major part of the evaluation for exploration and development in these parts of the delta. A formation sensitivity test consisting of the detailed study of the influence of various ions on the degree of formation damage of one of the main producing fields in the eastern Niger Delta has been studied. Analytical results of clay mineral composition obtained using X-ray diffraction (XRD) methodology were successfully applied to predict the various types of clay minerals present and hence intervals problem of shales. Further experimental formulations derived using Capillary Suction Time (CST) tests found that addition of 7% KCl to the original water based drilling fluid made drilling through the problem sequences easier leading to very good cost savings and compliance with the Nigerian environmental regulations. The operator has planned deeper drilling and further development of the field.Introduction and objectives Due to the increase in oil price and its cumulative usage, enhanced oil recovery (EOR) processes have been introduced worldwide in the last two decades. The capillary and viscous forces lead to oil recovery using the primary and secondary recovery processes, and the remaining trapped part of oil is produced. Since the new technologies emerged in oil industry for viscous oil recovery, the perspective of the world’s oil provision has been changed. Cyclic Steam Stimulation (CSS) is a thermal recovery method which is applied for heavy oil reservoirs. Other techniques include, in-Situ Combustion (ISC), Steam Assisted Gravity Drainage (SAGD), and Continuous Steam Injection ].Steam Assisted Gravity Drainage (SAGD) is one of the common thermal processes in which a pair of horizontal wells is drilled. This process was later modified to reach to higher efficiency values by introducing Fast SAGD, and NCG’s SAGD processes. In Fast-SAGD process, the system is equipped with offset wells using cyclic steam stimulation to increase the rate of growing the chamber sideway. The CSS process then begins at higher pressures in respect to SAGD wells. Following this approach, the steam chamber is grown laterally. In the present study, the effect of operating parameters including CSS well elevation, CSS well injection pressure and rate, CSS well starting time, spacing of SAGD wells and SAGD wells injection rate are studied on oil recovery factor. The optimum operating conditions is obtained using the CSOR and net present value (NPV) as the goal function.