Optimising the investments and de-risking development

Tracer technology is enabling informed decision making across the lifecycle of oil and gas fields globally. The demands of energy transition, combined with continued pressure to increase efficiencies and profitability, mean that understanding what is viable and knowing where to direct effort and re-source are essential.
As operators look to optimise their investments amid the confines of the energy transition, focus is on enhanced oil recovery from existing fields and tackling the challenges of unconventional extraction – both complex and ex-pensive endeavours.
In this article Tracerco presents two case studies demonstrating how tracer technologies are enabling optimised investments and de-risked development through the provision of accurate and actionable data for informed decision making.

Tracer technologies

Tracers are an established, proven technology that have been used in oil and gas production for over 60 years and can take multiple forms, from radioactive or chemical, solid, gas or liquid. Pumped into wells or positioned in completions, tracers help track the flow, presence and behaviour of liquids and gases throughout the production process. They are used to identify heat exchanger leaks, flow rates, flare studies and the performance of fluid catalytic cracking (FCC) units. Smart tracers are used to provide critical fluid flow insights in both conventional and unconventional reservoirs, allowing analysis of well and zone-specific production performance, at a fraction of the cost of alternative solutions such as production logging tools (PLT). This information can then be used to develop and maximise the full reservoir field potential, as well as increase in both conventional and non-conventional reservoirs. Chemical tracers were used in the case studies that follow.

Conventional application

The challenge

Following decades of production, an operator sought to improve the efficiency and maximise the productivity of its enhanced oil recovery (EOR) pro-gramme to maintain economic viability.
The operator sought to improve production using a water and gas (WAG) flood programme. Multiple water injectors were fixed along the exterior flanks of the field to provide a ‘water curtain’, used to contain any mobilised oil from moving outside of the unit. In an ideal scenario, injected CO2 would re-pressurise oil layers and dissolve into residual oil, decreasing its viscosity and increasing its mobility. However, the effectiveness of a CO2 flood can easily be skewed through the presence of fault systems, fracture networks, and complications beyond the wellbore that divert the injected gas and decrease sweep efficiency.
To combat this the operator turned to chemical tracers to help quantify the improvements from the new WAG program, confirm hypotheses about reservoir behaviour and fluid migration, and to support future project changes.

The solution

To better understand the reservoir architecture of its asset, the operator worked with Tracerco to apply specialty gas chemical tracers to the injected produced gas and CO2 as well as water chemical tracers to the injected water. By testing samples from select production wells, the company was able to establish where injected tracers, and by extension reservoir fluids, travelled within the reservoir. By measuring which production wells recovered the injected gas and water tracers, as well as breakthrough time, it was possible for the operator to:
Evaluate specific injector-to-producer flow connections.
Identify thief zones.
Identify the existence of faults or barriers to flow.
Additionally, the quantitative data provided by the tracers offered insight in how to rebalance the water and gas flood to better optimise the EOR strategy.

Operator value

Collected well samples quickly determined the flow paths of the injected gas and water across the network of the field. These results identified areas that required further investigation due to fast breakthrough as well as identifying water injectors that ineffectively added to the water curtain.
This streamlined data was invaluable in refining simulation models related to relative porosity and the extent of fracture systems within the field. Here, the tracer data established that much of the water introduced into one of the injectors was moving quickly and exclusively to one producer, resulting in a high produced water cut and undermining the effectiveness of the ‘water curtain’.
Based on these findings, this water injector was shut in, resulting in the surrounding production wells seeing far less water encroachment and more of a static pressure barrier from the injected water.
This change alone resulted in a 50% reduction in produced water while hydrocarbon production from the offset production well doubled. This allowed additional water capacity to be injected more effectively in other wells across the field.

The tracer data also revealed that one gas injector was disproportionately communicating with the producer compared to its peers. High gas rates produced in this well suggested a channel from one of the gas injectors and sparked an investigation into whether the offending gas injector could be choked or shut-in without reducing oil recovery. This injector circulated 50% of the injected gas to the producer whilst other injectors circulated less than 20%. The tracer data confirmed near-ideal flooding through the reservoir matrix, reflective of a highly fractured reservoir network. Data from the other producers indicated that all the injectors also supported the remaining associated producers and making changes to the injection would cause negative production impacts to those producers.

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Read the article online at: https://www.oilfieldtechnology.com/special-reports/07112024/optimising-the-investments-and-de-risking-development/