The innovation behind all of qWave’s tools and services is a shockwave generator system, the “qWave Pulser”, adapted to generate series of repeatable focused acoustic shockwaves for gradual generation of fractures/perforations in a wellbore wall, to improve existing perforations, initiate micro-fracs or removal of scale – without the need for any mechanical/rotating equipment or explosives.
The innovation is based on the same techniques as has been used in medicine for treatment of kidney stones for almost 40 years, utilizing electro source principles for generating series of repeatable focused acoustic shockwaves for gradual degeneration of the kidney stone.
The “qWave Pulser” mainly comprise a high voltage pulse generator, a shockwave generator source (e.g. electrohydraulic, piezoelectric or electromagnetic) and an acoustic shockwave focusing member (e.g. plane source, elliptic or parabolic shaped reflector), and will collectively form an integral platform in all of qWave tools.
The peak pressure within the focus area of the focused shockwave may be in the order of 10’s to 100’s MPa, hence, when repeated, holding enough energy to degenerate the toughest of materials.
Our first tool utilizes the qWave core technology for Micro-Frac Wireline operations. Pulse Generator Module inside the tool generates voltages upto 30,000 volts which creates a focused shock waves when released inside Reflector Module . These shock waves are focused on a point at the target rock, generating initial formation fractures – “qWave Perforation”
These initial formation fractures help in propagating hydraulic frac pressure beyond the near wellbore stresses which brings down the initial formation breakdown pressure, and hence achieving micro frac with more ease. The tool also contains a slow bleed off system which is used for determining fracture closure pressure in tight or impermeable formations.
- Liquid and pressure communication between a formation and a wellbore is often established or enhanced by perforation tunnels in the formation. Perforation tunnels are traditionally made using shaped charges of chemical explosives that inject a material into the formation, creating the tunnel.
- In conventional perforating, the explosive nature of the process shatters sand grains of the formation. A layer of “shock damaged region” having a permeability lower than that of the virgin formation matrix is typically formed around each perforation tunnel. The process may also generate a tunnel full of rock debris mixed in with the perforator charge debris. The shock damaged region and loose debris in the perforation tunnels are known to impair the productivity of production wells, or the injectivity of injector wells, and hence negatively impact upon the flow of liquids between the formation and the well.
The peak pressure exerted by an explosive shape charge is typically in the magnitude of 10k’s MPa, while only in the range of 10’s to 100’s MPa when exerted by the “qWave Pulser” technique. Therefore, the use of focused acoustic shock waves will cause significantly less damage to the formation, compared to using shaped explosive charges, while still exerting sufficient energy for a gradual, and gentle, excavation of new perforation tunnels. The relatively low energy excavation implies that the virgin permeability of the formation will not be compromised. Optionally keeping the wellbore in an underbalanced condition during all or parts of the perforation operation, and/or creating the perforation tunnels with an upwardly inclination may ensure cleaning of debris out from the perforation tunnels, having the advantage that debris will not impair the propagation of subsequent shock waves into the perforation tunnel thus leading to a more efficient excavation of the perforation tunnel.
Areas of Application
- Open hole perforation of water injection wells in hydrostatic pressure reservoirs: I.e. little to no option to backflush the formation prior to start of injection.
- Open hole perforation – production wells: For improved/enhanced fluid and pressure communication, especially in low permeability reservoirs, by generating tunnels/perforations bridging the area with drilling induced formation damage prior to setting lower completion, sand screens etc.
- Cased hole perforation: To perforate a cased hole section using the “qWave Pulser” technique would required the pre-step of a casing cutting member (such as a high energy laser, plasma cutting, water jet, mechanical tool etc.), to penetrate the steel casing, prior to using the “qWave Pulser” technique to generate a tunnel through the cement and into the formation.
Drilling induced formation damage, especially in low permeability reservoirs, cause challenges with regards to measuring accurate formation pressure and acquiring clean reservoir fluid samples.
- Using the “qWave Pulser” technique in combination with, or as a pre-step to, running a conventional downhole wireline formation tester, to enhance the coupling between the probe(s) of the wireline formation tester and the borehole, as well as enhancing the communication between the borehole and a more virgin formation, for improved measurement/sampling quality.
- Wells producing water are likely to develop deposits of inorganic scales. Scales can and do coat perforations, casing, production tubulars, valves, pumps, and downhole completion equipment, such as sand screens, safety equipment and gas lift mandrels. If allowed to proceed, this scaling will limit production, eventually requiring abandonment of the well.
- This limit in production may also be the result of poor perforation technique (high skin due to the “shock damaged region” caused by conventional perforation techniques), organic deposits in existing perforations (such as paraffin and asphaltene), clogging of sand screens etc..
- By way of high energy focused shockwaves, using the “qWave Pulser” technology, stimulate the areas affected for effective removal of scale, clogging or other deposits in the wellbore or downhole completion equipment, or improving (widening/extending) existing perforations having previously been created by conventional perforation techniques.
Areas of Application
- Cleaning and/or improving (widening/extending) existing perforations having previously been created by conventional perforation techniques.
- Cleaning of sand screens having been clogged by particles, scale or organic deposits.
- Removal of scale deposits from downhole completion equipment, such as downhole safety valves and gas lift mandrels.