Horizontal Well Completion for the Evaluation of Steam Soaked Wells
Authors: Mendoza H. A. , Briñez A. G. , Perozo H. A. , Aguirre W. A. 
Published: December 2007

Steam stimulation of reservoirs using horizontal wells has been suggested as a viable production method in the area of heavy crude within the basin area of Lake Maracaibo, Venezuela. To date, the accurate measurement of injection profiles have been both difficult and expensive requiring a well intervention to measure temperature, pressure and flow.

In addition, the very nature of an intervention means that the measured parameters may not accurately reflect the injection profiles under real conditions.

The purpose of this paper is to show how, with the use of an instrumented completion, we were able to evaluate the steam injection process under real-time conditions. The information gathered will allow hypotheses to be evaluated and more accurate predictions to be made regarding injection efficiencies in future wells. Important parameters to be estimated or inferred include the stimulated area, steam permeation into the reservoir and volume of steam injected. Detailed understanding of these parameters will allow for the optimization of the completion configuration for future horizontal wells.

The applied technology was installed in well LB 2644, Bachaquero field, a heavy crude field in the eastern onshore area, Lake Maracaibo. The sands of the reservoir are unconsolidated of deltaic origin corresponding to the Miocene age where approximately 10,300 MMBLS were deposited. The reservoir has been produced using steam soak stimulation with vertical wells for about 40 years with recoveries that vary from 20 to 35 %. With the arrival of horizontal drilling technology 4 years ago, 40 wells has been drilled which are being stimulated with the same steam process. Through the use of horizontal well technology it is anticipated that recovery can be improved by increasing the reservoir area contacted by the injected steam. The completion described allows for both steam injection and oil production and has been configured with permanently installed monitoring systems to allow for continuous monitoring of downhole conditions without requiring a well intervention. The downhole sensors were strapped to a tapering tubing string run along the length of the completion. Instrumentation included in the completion includes thermocouples for single point temperature readings; capillary tubing for single point pressure monitoring and a fibre optic system for monitoring distributed temperature along the total length of the completion.

The results show the advance of the steam front through the horizontal section, until complete steam stimulation of the whole horizontal well. Additionally, the results show the effects of injecting a commercial surfactant to observe its effect on the injection profile.

The completion design facilitates real-time monitoring of well characteristics during both injection and production phases without incurring the traditional additional direct and indirect costs normally encountered when carrying out a well intervention (direct logging costs and indirect costs of deferred oil production). The use of surfactants and their effects on the injection profile and/or production has not been observed in previous publications. The obtained results will confirm some hypotheses and further work will contribute to both the optimization of steam injection and completion configurations for new horizontal wells.