Rathlin Energy (UK) Ltd plans to use oil-based drilling fluids after data analyses showed that the formation was “very sensitive to aqueous fluids” at West Newton A and B sites in East Yorkshire.
DAMAGE
The operator said that lab analyses showed that previous drilling of the West Newton wells with water-based mud had created near wellbore damage in the Kirkham Abbey reservoir.
The damage was caused through the creation of very fine rock fragments while drilling, which potentially plug up the natural porosity and permeability of the reservoir and have a detrimental effect on its ability to flow, added Rathlin.
Diluted water-based acids would also have adversely affected the flow characteristics of the Kirkham Abbey reservoir.
The same tests demonstrated that drilling the Kirkham Abbey reservoir with an oil-based drilling fluid, could minimise the damage to the oil and gas reservoir.
Rathlin has now submitted applications to the Environment Agency for the use of oil-based drilling fluids within the oil and gas bearing Permian section, for both the West Newton sites.
HORIZONTAL WELLS
The company also commissioned RPS Group Ltd for a reservoir and completion programme.
RPS found that drilling with an oil-based mud system and extending the length of reservoir section penetrated by a well, would enhance the productive capability of each well.
Modelled wells extending up to 1,500 metres horizontally through the Kirkham Abbey would have a greater chance of encountering “significant sections of the reservoir with open natural fractures”, added Rathlin.
WORK PROGRAMME
The project’s technical teams are currently deciding the optimum orientation for a horizontal well from either the West Newton A or B site.
Rathlin has ordered long lead items such as steel casing for a horizontal well and is also assessing the availability of drilling rigs capable of drilling a 1,500m horizontal well.
GAS
Analyses of oil and gas samples from the wells and of mud gases measured during drilling show that the Kirkham Abbey reservoir contains gas (primarily methane 90% + ethane 5%) with associated light oil (condensate).
This could see a reduction is transportation of oil during production.
In June 2022, the company’s conceptual development plan focused mainly on gas with eight phased wells targeting 35 million barrels of oil equivalent.
Rathlin added that commercial production from West Newton could start as early as 2026.