Following the downturn, the number of horizontal wells drilled this year has fallen dramatically compared with previous historic levels. In these difficult times, attention to cost reduction through relentless optimization of all segments, from drilling to completions, has never been so important. Horizontal-well costs have decreased significantly over the last few years thanks to many lessons learned. In unconventional plays, multiple solutions have been implemented and tested in well construction, casing design, hole size, bottomhole assemblies (BHAs), directional systems, drillpipe, oscillation techniques, drill bits, well trajectory, and pad drilling, with the main goals being greater efficiency and reduction of costs.
On the drilling side, operators have been able to find the optimal drilling system to drill the curve and the lateral with the same BHA in just a few days. Have we reached a plateau? Not yet. Can we optimize more? Yes, absolutely. In unconventional wells, the trend is now to increase the horizontal length to 15,000 ft and, further, to increase the recoverability per foot of lateral. There is probably a technical and economic limit to this, but the industry has kept pushing these limits further. The role of digital technologies is increasing, and this enables oilfield performance improvements. Indeed, drilling data easily acquired now with electronic drilling recorders have revolutionized the possibility of visualization, monitoring, and analysis in real time. The attention recently has been on trying to use computer modeling to guide the directional-drilling process. Guidance systems in two or three dimensions are now helping the directional driller in real time to find the best possible well path to reduce tortuosity and maximize rate of penetration and possibly production. Data coming from the drilling job are now reused by completion teams to optimize the position of the hydraulic-fracturing stages to maximize production. The main idea consists of calculating the mechanical specific energy at the bit (derived from operating parameters) to estimate unconfined compressive strength of the rock, which is a valuable mechanical rock property for reservoir evaluation, eventually to map zones with high potential for fracturing.
Thanks to the analysis of previously drilled and completed wells (microseismic fracture mapping, reservoir modeling, and production analysis), the industry is moving toward optimal lateral and vertical spacing between two horizontal wells to get the greatest recovery of hydrocarbons in place.
On the completion side, the same data accumulated over the last few years have enabled operators to compare fairly the two typical completion systems used in unconventional plays (fracturing sleeve with activated ball or plug-and-perforate techniques) to better evaluate them and select one method over another.
These examples illustrate just a few of the numerous advances made in horizontal and complex-trajectory wells and demonstrate that, despite this historic downturn, the oil and gas industry has kept innovating and optimizing to bring more-efficient solutions to the table.
- spe.org: Journal Of Petroleum