An off-shore field in Abu-Dhabi has water injectors with dual completions injecting into 3 carbonate subzones A, B and C, separated by dense carbonate layers which act as impermeable barriers. Each completion has one of the two strings completed into two consecutive subzones. The irony is that subzone B is the most permeable and robs the other two of their injection quotas. This was occurring as the low permeability zones could not be acidized properly due to inefficient diversion. Repeated acidization of the commingled zones with benzoic acid diversion had not yielded desired results. In the on going inquest to select a positive diverter, a polymer based system was investigated as a diverting agent. This paper discusses the use of this polymer based acid activated diverting agent in staged stimulation's performed in injector wells in an off-shore field, Abu-Dhabi. The diversion mechanism is explained including how it compares with the other techniques. Polymer properties and characteristics are also explained. Introduction To ensure maximum damage removal and homogenous distribution of stimulation fluid occurs during treatments on multiple intervals of varying reservoir characteristics, it is necessary to divide the treatment into stages. A technique that forces each stage to go into a different zone is used during the procedure to assure treatment of the total productive interval. One of the most important factors affecting the success or failure of matrix stimulation treatments is the correct downhole placement of fluids for optimal zone coverage. When injected, these fluids naturally tend to follow the path of least resistance, that is to the higher permeability and/or least damaged zones. Since damage must be removed from the entire producing interval, effective diversion techniques must be employed. Previous techniques include; mechanical methods (zone isolation packers, packers and bridge plugs) for selective injection, are considered to be the most effective form of diversion, However, these tools generally require a rig on site. Ball sealers offer a cheaper and more practical approach but their effectiveness depends on many parameters including, the length of the perforated interval(s), roundness and smoothness of the perforation holes, injection rate and the differential pressures across the perforations. Particulate diverters like graded rock salt (GRS) and benzoic acid flakes (BAF) enable the flow to be diverted by depositing a cake on the reservoir rock face, thereby generating a temporary skin factor. P. 503

This paper demonstrates the value of collecting and interpreting real-time data for reservoir surveillance. We present three examples of real-time data acquisition and interpretation. The first example shows how formation pressure while drilling (FPWD) data provides permeability quantification for placement of a horizontal lateral. Initial performance of the pilot injector confirmed optimum placement of the well demonstrating value of information (VOI) from real-time data acquisition. In addition, pressure data helped in understanding the pressure distribution along the lateral due to support from a nearby gas injector and also in adjustment of mud parameters for drilling. The second example highlights the use of downhole fluid analysis (DFA) to confirm gas breakthrough detected earlier by open hole logs, to estimate gas oil ratio of the producer and help selection of fluid sampling point. Integrated analysis of logs, modular formation-dynamics tester (MDT) pressures, DFA results, flow test data and subsequent PVT analysis of oil provided indication of complex gas movement from injector to producer and provided insight on vertical sweep of gas. The third example demonstrates the use of permanent downhole gauges (PDHG) data for real-time performance monitoring of a maximum reservoir contact (MRC) well. Results of the analysis show clear evidence of voidage balance from nearby MRC injector and underscore the feasibility of field development with water injection in a lower permeability area. Combining the effective well length derived from production logging tool (PLT) data, the example also illustrates pressure /rate deconvolution analysis to determine permeability and skin. Additionally, rate-transient analysis (RTA) is done using rate and high-frequency long-term pressure data to compute permeability, skin and drainage area of the well.

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