minimising increasing costs, production efficiency must be at least maintained, and ... Some solutions may have to be in
Chris Marland, Halliburton, USA, investigates engineered solutions designed to help maximise productivity with a holistic approach to well construction.
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s margins are continually squeezed, operators are looking for ways to maintain and increase profitability to continue long‑term investments. From production platforms and support vessels in offshore markets, to new infrastructure such as roads, housing and pipelines in land markets, exploration and production activities demand continuous investment. To maintain and increase revenues while minimising increasing costs, production efficiency must be at least maintained, and preferably increased, to account for inflationary pressures. But how? With so many varied factors contributing to reservoir performance, maximising production requires operators to take a holistic view of every aspect of well construction and delivery.
Many paths to productivity
Productivity can be viewed in many ways. Employing technology to increase hydrocarbon recovery using existing technology is an obvious path. Production increases are often achieved by increasing the length of the exposed payzone or by modifying the well trajectory to intersect the reservoir at a more favourable location. Production can also be increased with the development and implementation of new completion and stimulation techniques. Hydraulic fracturing (fracking), in particular, has developed to serve growing unconventional markets. Now, many companies offer a range of fracking solutions to enhance productivity while reducing environmental impact and project costs. New technology, such as solar-powered vertical proppant storage and delivery vehicles, have not only reduced diesel costs and but also the risk of leaks, emissions and the footprint on location. Additionally, research into the swelling properties of different elastomers, especially when in contact with hydrocarbons, has led to innovations and improvements in downhole packer and zonal isolation designs. Stimulation options now range from hydraulic fracturing to acidising.
Of course, successful fracturing requires planning; and the results show the effort is worthwhile. Enhancements in fracture engineering have driven a significant increase in productivity and ROI that typically outweighs the cost of fracking. In one such example, the cost to upgrade a fracking system was significant, but the resulting revenue increase was over five times the expense. Much attention has been paid to productivity improvement delivered by directly increasing production in reservoirs that have already been drilled. It is natural for the focus on maximising production to be on the later stages of well construction. However, there are as many, if not more, opportunities to improve production and avoid negative impacts on production to be found in the drilling process. (Note that the drilling process can negatively impact productivity in ways that stimulation or other production techniques cannot rectify). These opportunities are waiting to be uncovered during the pre-planning process.
Reservoir damage
Reservoir damage caused by drilling includes mechanical or hydrodynamic enlarging that makes it difficult to effectively seal off zones or apply stimulation to others. Solids in the drilling fluid can plug pore spaces, as can clay swelling or dispersion where reservoirs contain water-sensitive clays. The challenge to minimise and even eliminate such reservoir damage is an important part of drilling engineering planning phase of a project. The impact of the potential damage needs to be clearly understood from the beginning, since in many cases these effects cannot be fully reversed and may irreparably alter the production schedule.
Time management
Delivering reservoir fluids to production is what generates revenue. Therefore, it would seem obvious that reducing the time to production would be the goal of any operator. Reducing time to production includes reducing drilling and casing time, which in turn means increasing drilling efficiency and rate of penetration (ROP). In addition, non-productive time (NPT) and invisible lost time (ILT) must be reduced. Many independent and national oil companies have yearly NPT targets, with focus groups tasked to identify and make improvements. Despite such efforts, industry NPT continues to average 20 to 25% of all well costs, while ILT spent conducting necessary operations inefficiently accounts for around 15% of well costs.1 In terms of improving drilling metrics, addressing NPT and ILT requires sound planning and execution. Effective knowledge-capture during and after drilling is key to ensuring lessons learned are shared and used. Traditional end-of-well reports delivered two to three weeks after a well are rarely effective for knowledge sharing; rather, what is needed is a system where the data from well construction is integrated and made accessible in a timely manner. With lessons learnt readily available, drilling engineering planning can incorporate this knowledge to improve performance and reduce the likelihood of NPT and ILT on subsequent wells. While this iterative process signifies a ‘holistic view’ that optimises drilling operations; maximising reservoir production requires a holistic approach that optimises ‘end-to-end’ performance through focused engineered solutions.
Drilling engineering solutions
Solutions that encompass planning, preparation, execution and knowledge capture using end-to-end service delivery are best provided by an engineering solutions team formed to address this specific business requirement. Linking the key drilling offerings – directional drilling and measurements, fluid services and bit/reamer products – brings a holistic approach to the drilling engineering challenges affecting performance and
| Oilfield Technology Reprinted from July 2014
well productivity. Similarly, focused engineering solutions should be able to address the specific engineering needs of different well challenges and complexities. Some solutions may have to be integrated into the design process at a very early phase, sometimes prior to rig selection. Others are more relevant to mitigating risk while drilling the well. This range of needs suggests there may be benefit in tiered-solution offerings that can be integrated at different points in the well design process.
Reducing risk and uncertainty
While planning serves to mitigate risk by preparing for known or expected problems, uncertainty still remains during drilling and tripping in and out of the hole. In particular, geological uncertainty can result in unexpected bottom hole assembly (BHA) performance, leading to directional drilling challenges or formation pressure uncertainty. While pore pressure‑while‑drilling measurement tools are becoming more common, they measure pressure in permeable formations that already have been drilled. What is needed, especially in exploration environments, is forecasting of geopressures with updates and model corrections, to predict ahead of the bit. Even in development projects, pressure surprises can occur. On the 21st well of a development in Eastern Canada, unexpected high pressure caused a well control situation. Formal review of the data showed real time prediction would have identified the pressure ramp through overlying shale sequences, and may have let the operator remediate the influx with a more suitable mud weight. Similarly, deepwater environments can encounter ballooning or wellbore breathing behaviour, whereby the formation absorbs drilling fluids when the pumps are on and returns the fluids to the annulus when the pumps are off, which is difficult to predict without suitable offset data, and may not be encountered in all wells. Nevertheless, incorrect identification of this phenomenon can lead to incorrect mitigation, and worsen, rather than effectively manage the situation. In these instances, a focused engineered solution, including risk mitigation with specialist expertise, improves real time drilling performance.
Incremental performance improvements
These solutions can also support performance improvement by identifying limiters to ROP, or addressing operating parameters that are not being effectively applied. Examples include delaying an increase in mud weight should formation pressure not increase as quickly or to the level predicted, identifying specific operating parameters to manage bit wear through certain formations (thus extending bit life) and defining when previously standard hole cleaning or circulating practices are not required, thus eliminating unnecessary operations. While these incremental improvements may be harder to quantify, each can and does positively impact well delivery time. While each may only have a small impact on overall time, the less time spent drilling, circulating, or reaming, the less likely are associated wellbore problems. In most cases risk mitigation or performance improvements like these are delivered by managing resources already actively being used in the wellbore or available at the rig site. While land work may lend itself to more flexible logistics, both offshore and onshore locations are somewhat restrictive in supporting radical changes to drilling equipment, emphasising the importance of in-depth planning.
Integrated, in-depth planning
More significant drilling performance improvement and assurance are delivered by in-depth integrated planning and technical
feasibility studies. These require involvement early in the planning process – prior to ordering BHA, bits, reamers, fluids and other equipment key to the drilling process. A full review of BHA and bit/reamer designs using offset analysis, performance metrics, and engineering for a field will deliver the optimum design for a given well’s challenges. Bit design and configuration can be matched with new technology or improvements in bit durability to extend drilling life; although it should be noted that these choices may require months to get designs in place and built. Likewise, drilling procedures can be optimised and tailored to, for example, balance the need for instantaneous ROP improvement with longevity to avoid early and unnecessary tripping. Including a full review of fluid design alongside the expected drilling pressure window enables an even more holistic approach to the planning process. Fluids are a major cost component in every well programme and have significant effect on the entire system. Aside from primary well control they are responsible for hole cleaning, formation stability, MWD telemetry, BHA lubrication and hydraulic energy transfer through the bit, amongst others. A holistic approach clearly must incorporate fluid system design. In one example from the UK, an engineered solution combining a new drilling system designed for the area, a matched bit and engineered drilling fluid resulted in well delivery 25 days ahead of plan. This not only reduced rig costs through time reduction, but the excellent quality of the wellbore and resulting MWD measurement also eliminated the need for costly wireline logging. Clearly, an engineered solution can have significant impact on well delivery costs, and can maximise productivity of the drilling phase by enabling earlier production.
Unconventional challenges
In areas of complex geology or formation pressure abnormalities, where conventional drilling cannot be used or is too risky, additional drilling assurance measures are needed to more effectively manage the pressure system and facilitate production. Narrow pressure windows that are unmanageable with conventional fluid and pressure management, or highly compartmentalised reservoirs where production may have caused significant pressure differences between zones, are challenges that may require underbalanced or managed pressure drilling. This process requires extensive front-end planning and evaluation of well and reservoir designs, and the geological and fluid environment. With planning and correct implementation, pressure optimisation solutions can dramatically improve well delivery success and reservoir performance. In one such example from China, an operator wanted to avoid historical lost circulation, frequent gas kicks and reservoir contamination. After thorough evaluation and a technical feasibility study, a managed pressure drilling solution was implemented that reduced drilling time by 18 days and delivered the longest lateral section ever drilled there without reservoir contamination. In this example, the benefits of more advanced engineering and deployment of specialist equipment include improved drilling and reservoir productivity as well as reduced costs.
Optimised field planning and wellbore placement
Further gains in reservoir productivity can be achieved by field planning to more effectively drain the reservoir with fewer or better-designed wells, or both. Field planning, especially with a high number of well designs, can be time consuming – sometimes to the point of impacting well delivery schedules. This can be costly, as drilling, logistics and eventual production are all delayed while costs continue to mount. With a
dedicated engineering team using the most advanced technology, such delays can be avoided and well planning cycles can be significantly reduced. An operator in Canada trying to plan 10 pads with 80 horizontal wellbores was taking more than 180 days to complete two planning iterations. A solution was found that reduced the same planning requirements to 15 days but with 30 iterations. With knowledge captured from that session, planning the next play cut a further 80% off that time. The time savings reduced drilling cost an average of 13% across the first play with greater savings anticipated on the second play. To impact ultimate well productivity, engineered well planning must be supplemented by accurate well placement. Well placement in complex reservoirs typically requires geosteering to penetrate various formations while minimising well path changes and staying within the zone of interest. Geosteering requires advanced modelling using offset wells to define the formation evaluation responses associated with the reservoir and bounding formations. It may also require more specialised tools, with the planning and evaluation process identifying the best fit-for-purpose technology, which may include an azimuthally focused tool or sonic measurements. Nevertheless, geosteering solutions can drive significant reservoir production improvements, especially in unconventional plays when a shale formation may have a thin ‘sweet spot’ within which production is significantly improved. An operator in Mexico realised this benefit by using a geosteering solution through a 10 ft thick production zone. Effective geosteering exposed the entire 4300 ft of lateral to the shale reservoir and delivered the wellbore 16 days ahead of plan. In this case, the double benefit of drilling time reduction and greater reservoir exposure served to maximise reservoir productivity, and therefore revenue, while also reducing cost of well delivery. It also brought production online earlier, which meant revenue and profitability were realised at an earlier stage in the asset development.
The big picture of productivity
From field planning that optimises well placement, through BHA modelling that improves drilling performance, to completion and stimulation techniques that extend reservoir life, maximising the productivity of assets requires a holistic view of every aspect of well construction and delivery. Although each party may have one area of focus, it is incumbent upon the industry to move toward a model where operators and service companies share ownership of asset performance through focused engineered solutions. While operational silos still exist, especially between the drilling team and the completion and production team, complete performance improvement for an asset cannot be achieved without all parties involved understanding the others’ requirements and working together to maximise results. As operators and service companies increasingly recognise the value of taking a holistic approach in enhancing production levels and advancing the industry, it should be expected that far greater engagement from more advanced engineering solutions will occur far earlier in the process. To keep pace with the ever growing need for energy, the growth in engineered solutions will likely accelerate, along with expansion of the industry’s technical capabilities through the second half of this decade. Engineered solutions using a holistic approach to well construction through delivery will help realise the improved economics needed in this ever-challenging economic environment.
References 1.
‘Downhole Drilling Problems: Drilling Mysteries Revealed!’ AAPL 58th Annual Meeting (June 2012).
Reprinted from July 2014 Oilfield Technology |
