Tracerco logo

Case Study

Long-Term Water Breakthrough Measurement in a Bilateral Wellbore Using Tracer Technology

The Project

An offshore oilfield was developed using long multilateral horizontal wells completed with swell packers and stand-alone sand screens. To assist with recovery of hydrocarbons, seawater injection was used in four horizontal injection wells throughout the development area. As part of the overall reservoir management strategy the operator wanted a method to determine the source of seawater breakthrough and the positional in-flow of water into production wells.

Project Design
The project was designed to deliver:

  • Unique interwell tracers to measure communication pathways and sweep efficiencies between wells
  • Long term dormant water tracers integrated into sand screens to measure positional water in-flow
  • Significant cost savings over other wellbore surveillance technologies
  • Zero additional rig time
Reservoir & Well Specification
  • Sandstone reservoir
  • 21 API Oil
  • 1,200 metre bilateral horizontal production length
  • 5 1/2" premium sand screens c/w swell packers
  • Reservoir Temperature and Pressure; 174°F / 2830psi
Application of the Technology
Four unique long term water tracers were manufactured in solid polymer form and integrated into the drainage layer of wire wrap sand screens during their manufacture. There was no requirement to change sand screen size or design. The tracer - polymer mix was designed to remain dormant during oil contact and start to slowly release upon contact with water. Each of the sand screens was labelled with the specific tracer material to be referenced when running in hole. In addition to sand screen tracers, four unique waterflood tracers were manufactured and made ready for injection.

Long term water breakthrough measurement

Sand screens containing tracer materials were transported along with all other standard screens offshore. Each one was unwrapped from its protective seal and placed within the lower completion run sequence to locate it at specific points along the two laterals. Two of the tracers were located approximately two-thirds of the distance along each lateral with the other two positioned around one-third from the heel of each.

After each water injection well was brought on-stream and stabilised over a few weeks, waterflood tracer was added directly into the flow line using high pressure hydraulic pumps over several hours with no disruption to normal waterflood operations.

Sampling and Analysis
Production wells were tested once every two weeks to determine water cut. Upon detection of water breakthrough from each well a very small volume of water was taken and sent to the nearest Tracerco laboratory for tracer analysis using ultra-sensitive Gas Chromatography instrumentation and optimised tracer detection methodology.

Controlled release tracer response vs accumulated produced water volume

Results and Interpretation The graphical data shown relates to one of the production wells. This well started to increase water cut approximately 48 weeks after start of production (1). Tracer was detected after 52 weeks (2) originating from the lower one-third of lateral 2. Confirmation of the source of the water started to emerge after 57 weeks (3) showing injector C communication. The heel of lateral 1 was next detected after 80 weeks of production (4) followed by the interwell tracer injected into Injector A (5). It was also noted that tracer located towards the heel of lateral 2 was detected at the surface although its shape was somewhat flat (6). It is believed that this is due to slight internal contact between water flowing inside the production tubing from the toe of the well accessing the heel tracer through the perforated base pipe providing limited but direct contact with tracer in the drainage layer.

Data provided by the application of both interwell and inflow tracer technologies has provided valuable information on injected water communication pathways and effectiveness of hydrocarbon sweep within the reservoir strata. This has allowed the rebalancing of injection water to minimise water production and maximise reservoir fluid contact.

For more information about this technology please fill out an enquiry form detailing your requirements and we will get back to you.

Johnson Matthey Logo