Article featured in Harts E&P

In recent years, the Permian basin is been the most prolific shale play in the US. Production in this area increased to 3.8 million barrels by 2019, representing almost 70% of the whole US production growth from 2011 to 2019 according to International Energy Agency (IEA). The impressive aspect of this achievement is that the growth has not stopped. On the contrary, the Permian is expected to continue growing and is estimated to achieve up to 5.8 million barrels by the end of 2023.

Such impressive growth doesn’t come easy. Significant advances in drilling, completing and multi-stage fracturing will continue to drive production increases. But evaluating the performance of fracturing programmes and the wells they deliver is key to optimising resources and ensuring maximum return on investment. Conventional diagnostics [such as production logging tools or ‘PLT’s’] can’t provide all the insights required to ensure the operator is achieving the best returns. This article focuses on the challenges faced when assessing unconventional reservoirs in terms of production, and features a new diagnostic capability introduced by TGT to evaluate the flow performance of hydraulically fractured wells, stage-by-stage. The new diagnostic product is aptly called ‘Fracture Flow’.

Operators have been drilling aggressively and pushing the boundaries of hydraulic fracturing beyond conventional standards compared to other plays. The drilled length of lateral sections has been constantly boosted, adding more footage as well as more production stages. The ultimate objective is to penetrate deep into the target formation increasing the area of contact with the specific reservoir or formation making the well, its completion and the reservoir one dynamic production system.

Champions of this approach include a Houston-based operator that recently drilled such a well at the Wolfcamp. The completion included a lateral section of more than 17,900 ft running through the Spaberry formation. The completed well had a total measured depth exceeding 24,500 ft with a customised completion design and fracking treatment. The completion included more than 50-stages and sand was pumped along more than 2,200 ft of reservoir to increase the well productivity.

These extended laterals have been engineered to optimise production performance and leverage improvements in drilling, fracking treatments and completion designs. The operators have overcome the number of well construction challenges and have quickly moved up a steep learning curve.

Like the challenges encountered with well construction, the Permian basin faces its own challenges. Following such an extensive multistage hydraulic fracturing programme, the wells are brought onstream at high initial production rates. But most of these extended-lateral producers tend to decline dramatically over a very short period. To help combat this challenge, and many others, TGT has developed a number of application-specific diagnostic products using its ‘True Flow System’ to quantitively evaluate flow dynamics throughout the entire well system – from reservoir to the wellbore, and the dynamic interplay between the two.

When talking about a hydraulic fracturing job, we all know the importance of the programme design prior to execution. During this phase, sophisticated software is utilised to model and optimise the fracturing programme, taking into consideration multiple variables. These variables include formation properties, lithology, depth, mechanical stresses and other parameters that can affect the final outcome. Another important consideration is the formulation of the hydraulic fracturing fluid. This fluid is normally comprised of sand (or proppant), gels (foam or sleek-water) and additives that are pumped downhole following the job design to prop open the induced fractures and maximise the extension of the fracture in terms of length, height and aperture as well as the integrity of the fractured conduit itself, so hydrocarbons can flow unabated.

TGT’s diagnostic ‘Fracture Flow’ product is able to locate and evaluate fracture inflows and quantify inflow profiles in hydraulically fractured wells. The product is delivered by our analysts using the ‘True Flow System’, which combines several technology platforms – Chorus (acoustic), Cascade (thermal), Indigo (multisense) and Maxim (digital workspace), to acquire, interrogate and analyse the acoustic spectra and temperature changes generated by the hydrocarbons or any other fluid flowing from the reservoir through active fractures and into the completion. This diagnostic capability goes beyond conventional flow measurement techniques that generally stop sensing at the wellbore and are therefore unable to quantify flow within the reservoir itself.

The Fracture Flow product extract shown in figure-1 represents the diagnosis of a hydraulically fractured oil producer with >80 degrees deviation. The reservoir has a gross thickness of approximately 1,200 ft and is fully cased.