Data driven well models were constructed for a steam injected field producing 800 m3/d of API 8 bitumen from 100+ beam pumped wells. The modelling technique is known as Production Universe(PU) which gives real time estimates of oil and water flows for each of the wells during steady state and transient operations. PU tracks rates when wells are starting-up, closing-in and for transient flow oscillations, resulting in automatic daily reports of total production and deferment (low and off) for each well.
The deferments reports drive an exception-based surveillance (EBS) process by flagging the engineers of the largest production gain opportunities. EBS analysis and associated well remedial actions have resulted in an 8% production gain.
Continuous estimation of well bitumen and water flows has allowed real time optimization of the entire field. This is achieved by continuously maximizing production within the plant water handling and economic constraints. The system knows how much oil and water the wells are producing and recommends rates for each of the wells to maximize production within the water handling capability.
The EBS process has been successfully running for more than a year. The RTO process has just been introduced, hence it is too early to estimate the incremental gain.
This paper will detail the surveillance and optimization techniques, learnings and associated work processes.
Background and Field Description
The field is located in Northern Alberta, Canada and produces 1,200 m3/day of API 8 bitumen with an in-situ viscosity of 100,000 cp at reservoir pressure. The production facility consists of 8 production pads, each with 8 -16 wells.
Steam injection is used to reduce the bitumen viscosity such that it can flow to the well bores. Bitumen and water have similar densities at operational temperatures. The wells operate in a cyclic steam stimulation mode and steam drive mode. In CSS steam is injected into each well at a given rate for a given time, after which natural production commences, without artificial lift with temperatures in excess of 200 degrees C. Once the pressure drops below a certain level, rod pump artificial lift commences and continues until the temperature falls to a level that does not support adequate flow rates and steam injection again commences and the cycle repeats. In steam drive steam is continuously injected via dedicated injectors to mobilize bitumen and drive it to the adjacent producers.
During the CSS production phase and in steam drive, bitumen is rod-pumped (or flows naturally) as an emulsion to the treatment plant. Treatment consists of degassing, separating into bitumen/ water phases and spiking with diluent to allow effective pipeline transportation to the refinery. The produced gas is compressed and injected into the formation for future usage. Produced water is disposed off via water disposal wells.
During the production phase well tests are performed frequently.
Graphical depictions of the field location and the overall process flow are shown in the following diagrams.