How multilateral wells are unlocking reserves in legacy oil pools 

New analysis from Geologic highlights how multilateral wells (MLWs) may help recover bypassed/unswept oil, add incremental reserves, and improve late-life performance in mature oil pools.

The findings point to a redevelopment opportunity in Alberta and Saskatchewan, where operators are increasingly looking at their existing assets for lower-risk reserve growth. 

Waterflooding has long been used to maintain reservoir pressure and improve recovery, but over time it can leave significant volumes of oil stranded near in the reservoir.

In mature heavy oil pools poorly drained areas, especially the fringe areas where oil has been pushed to from the effects of the waterflood, may still contain recoverable barrels that conventional vertical wells are unlikely to reach effectively.

Targeting bypassed oil at the edges of mature waterfloods

Multilateral wells are designed to address that challenge by increasing reservoir contact from a single surface location, allowing producers to reach undrained areas and recover oil that legacy vertical wells missed. 

The analysis focuses on MLW development along the periphery of mature waterfloods, where oil has been displaced but not fully produced.

In these settings, the approach offers a way to target previously stranded volumes without moving to more complex enhanced recovery methods. 

This MLW redevelopment technique has been shown to also be effective on legacy oil pools that are under primary production.  

Early results point to production and recovery upside

Case studies from several pools in the Mannville Group formations point to a number of consistent outcomes: 

• MLWs delivered higher initial oil production rates compared with legacy wells 

• Water cuts were significantly lower, indicating cleaner oil production 

• Sustained production over multiple years confirms access to bypassed oil on the fringes of oil pools

• Recovery factor improvements of around 10% were observed in studied pools  

At a broader level, production data suggests MLW deployment can help reverse late-life declines in mature waterfloods. In a high-level look at composite production data for the entire Mannville Stack play, MLW development (which started in mid-2020) increased production from roughly 175 mbbl/d to about 203 mbbl/d, while watercut and GOR trends also improved.   

On a smaller scale, when the Wildmere Commingled Pool 001 was studied, four MLWs drilled on the fringes of that legacy waterflooded pool (comprising a total of 40 legs, 24.6 km of exposure to the Lloydminster member), produced over 380 mbbl of oil in under 45 months. The 13-leg (9.6 km) well drilled on the SE flank of the pool had an initial production of 359 bbl/d.

Broader upside across a largely underdeveloped pool inventory

The MLW redevelopment case extends well beyond individual examples. 

Across Alberta, Geologic identified 261 producing, non-commingled oil pools with cumulative production greater than 5 mmbbl after screening out inactive and commingled assets. Of the 130 Cretaceous pools in that set, only seven include multilateral wells with four or more legs beyond the Clearwater play – which speaks to the upside opportunity for this type of redevelopment). 

That limited adoption helps frame the broader opportunity. In the top 10 Cretaceous pools alone, Geologic estimates that a 5% uplift in recovery factor would equate to roughly 603 million bbls of incremental oil, while a 10% uplift would exceed 1.2 billion bbls. Even modest recovery gains, if repeatable across a wider inventory, could translate into meaningful reserve additions and longer field life. 

What the analysis suggests for redevelopment strategy

The analysis positions MLWs as a middle ground between leaving mature pools largely undeveloped and moving to more capital-intensive enhanced oil recovery methods. 

Several practical screening considerations emerge from the work: 

• Prioritizing mature pools with evidence of bypassed oil at the margins 

• Using historical production and waterflood performance to identify candidates 

• Designing wells with longer lateral exposure and precise placement to maximize contact with undrained zones 

• Maintaining reservoir pressure to support long-term production performance  

Extending the productive life of legacy assets

As new discoveries become harder to find, more attention is shifting toward maximizing recovery from existing assets. In that context, MLW development appears increasingly relevant for mature conventional oil portfolios where bypassed oil remains in place. 

Geologic’s analysis suggests multilateral well redevelopment can contribute to that strategy by unlocking previously unrecovered oil, supporting reserve growth and extending field life without fundamentally changing the operating model of these assets. 

Taken together, the results suggest multilateral wells could become an increasingly important redevelopment tool in mature pools, particularly where legacy waterflooding has left recoverable oil on the fringes of a reservoir.