A Shallow Plugging-Selective Re-Entry Technique for Profile Correction

Abstract

This paper presents a new technique for correcting wellbore profiles. This shallow plugging-selective re-entry technique has the potential to increase supplemental oil recovery and to reduce operating costs. Both laboratory and field experiments show the technique to be a valid approach to profile correction. Introduction Control of wellbore injection and production profiles is a prerequisite for efficient execution of supplemental prerequisite for efficient execution of supplemental recovery projects. For example, in a waterflood, poor profiles may lead to early water breakthrough and bypassed profiles may lead to early water breakthrough and bypassed oil. Furthermore, they may lead to excessive water production. This results in high lifting and disposal costs in production. This results in high lifting and disposal costs in addition to unnecessary backpressure on oil-producing zones if the well cannot be pumped off. Poor profiles are potentially more serious when expensive tertiary potentially more serious when expensive tertiary recovery fluids are lost in nontarget zones. The lack of technology for correcting many inadequate profiles results in reduced profitability of supplemental recovery projects and may even lead to their abandonment before maximum oil recovery. Profile problems are expected to increase in number and severity as producing fields become older and the emphasis on secondary and tertiary recovery increases. This paper discusses a new approach to correction of wellbore profiles. Shell is developing a shallow plugging-selective re-entry technique that appears plugging-selective re-entry technique that appears promising. By disseminating our information on this approach promising. By disseminating our information on this approach to those who face similar problems, we hope to accelerate its evaluation and, in general, encourage development of profile correction techniques. profile correction techniques. Problem Analysis, Background, and Problem Analysis, Background, and Requirements Most problems with profile correction occur in commingled multizone completions. Individual zones in communication with a wellbore often have different reservoir characteristics such as permeability, fluid content, pressure, and impairment. Consequently, their receptivities pressure, and impairment. Consequently, their receptivities or productivities differ. The resulting profile may be the desired one; that is, it is consistent with planned zonal injection or withdrawal. However, the opposite is most often the case. Good wellbore profiles by themselves do not necessarily result in the desired vertical flooding pattern. The flow profile in or immediately around the wellbore is only significant in terms of flood performance if this profile correlates with the vertical flooding pattern away from the wellbore. Whether such a correlation is likely to occur generally can be determined by geological study. Once a flood is in progress, vertical sweep efficiency may be diagnosed from its progress, vertical sweep efficiency may be diagnosed from its performance. In this paper, the significance of wellbore profiles performance. In this paper, the significance of wellbore profiles is assumed. Remedial efforts to correct profiles are seriously hampered by lack of zonal isolation in the wellbore. Open-hole or uncemented liner completions and inadequate or deteriorated annular cement often prevent the selective placement of plugging materials. If attempted under placement of plugging materials. If attempted under these conditions, damage to adjoining zones often cannot be avoided. Shell's success with selective placement of plugging fluids for profile correction in these types of plugging fluids for profile correction in these types of wells has been poor. The general approach to profile correction is to place selectively a plugging fluid into the target zones after these zones have been isolated from adjoining zones through the use of packers or a temporary sand plug. JPT P. 571