Evaluating Expandable Tubular Zonal And Swelling Elastomer Isolation Using Wireline Ultrasonic Measurements

Abstract

New completion techniques using expandable casing with swelling elastomers to seal the annulus, or just swelling elastomers used as packers are becoming available. Diagnostic services are required for these new completions such as evaluation of the annular seal, analogous to cement evaluation. Both conventional and new generation Wireline ultrasonic measurements have been used to characterize and possibly evaluate zonal isolation using swellable elastomers. So far, the following 360 degs circumferential measurements were studied: Ultrasonic radii, acoustic impedance (AI), as well as attenuation and third interface Echo (TIE) reflections from flexural wave data. Radii measurements show a "springback" effect, indicating that expansion against the formation has been achieved. Flexural attenuation has a much better dynamic range over the elastomer sections compared to the acoustic impedance measurements. Both measurements do not consistently distinguish rubber-backed casing with ordinary casing in our examples. The TIE from the latest generation imaging tool tracking the external rubber interface, may provide the measurement the industry needs. First results look promising and further experiments to characterize the tool response are ongoing. The casing geometry of expanded liners was also studied. Introduction The introduction of expandable metal technology and new "smart" materials like swelling elastomers will provide more options for well construction and completion:New techniques in zonal isolation are now possible for over - underpressured, fractured zones and zones with fluid losses [1], [2],Allowing monobore well design [3],Production of selected zones will be made easier, like selective perforation, completion, and stimulation [4],Multilateral junction sealing will be made easier. The effectiveness of zonal isolation and long-term well integrity for this new technology needs to be evaluated and proven. " Smart Material" - Swelling Elastomers Swelling elastomers are now offered by several service companies and have been used by operators for a variety of applications: As a means to establish zonal isolation in liner completions where conventionally a cement column would be used [5], as a production separation packer (swelling packers are used to replace conventional hydraulically or mechanically set packers) [6], and as an integral part of an expandable open hole clad [1]. By incorporating filler materials into an elastomeric matrix the material reacts or swells with time if in contact with water, depending on the elastomer and the requirements [7]. A water swellable elastomer swells through the absorption of (saline) water (osmosis process). An oil swellable elastomer swells primarily through the absorption of hydrocarbons (diffusion process). The typical swelling ratio is about 1.75 to 2.5 and swelling pressures are up to 150 bar. Swelling time is from 5–100 days depending on produced water salinity, temperature and oil viscosity and composition. The longevity of swelling elastomers still has to be quantified.

Understanding acoustic methods for cement bond logging

“…In the last decade, a pitch-catch method was introduced for the cement bonding evaluation (e.g., van Kuijk et al, 2005;Herold et al, 2006;Morris et al, 2007;Froelich, 2008). The tool in the field application, combining the pulse-echo and ultrasonic flexural techniques, provides the echo from the casing and the reflections from third acoustic interface (interface between filled material and rock in a single casing model).…”

Mechanical and structural behavior of a swelling elastomer under compressive loading

“…Swelling rate for a specific elastomer depends on the temperature and composition of the swelling medium. Water-swelling elastomers swell through absorption of saline water following the mechanism of osmosis, while oil-swelling elastomers swell by absorption of hydrocarbons through a diffusion process [5]. Elastomers have low modulus of elasticity (E) ranging from 10 MPa to 4 GPa (E-value for most metals is in the 50-400 GPa range), but very high elongation reaching up to 1000% (elongation for metals is always less than 100%).…”

Evaluation of Water Swelling Elastomers

“…3 Zone isolation in long horizontal wells is a difficult task. 6 It is important to not locate and set the swelling packers in holes with potential washout because if the hole size is more than the swelling envelope of the packer it will not seal properly. For example, in case of premature water production when using slotted liner completion, the liner has to be plugged back with cement to shut-off the water.…”

“…Bonding forces between individual molecules and polymer molecules are provided by the valence electrons. 6 The concept behind oil swelling packers is the absorption of oil when it comes in contact with the elastomeric material in the packers. 8 While rubber compounds that swell with oil are well known, new rubbers were recently indtroduced that swell with water.…”

“…Practically, swellable packers need 5-100 days to complete the swelling process. 6 The objectives of the present study are to: (1) Examine water swelling packers in different brines (2) Assess the effect of 15 wt% HCl acid on the swelled elastomers, (3) Determine the effect of water on elastomers that were exposed to 15 wt% HCl acid, and (4) Assess the effect of brines on swelled elastomers. 6 The concept behind oil swelling packers is the absorption of oil when it comes in contact with the elastomeric material in the packers.…”