DURABILITY OF PERFORATED GFRP UNDER VARIOUS ENVIRONMENTAL CONDITIONS WITH EMPHASIS ON ITS APPLICATION AS A LINER FOR DIRECTIONAL OIL WELLS

Abstract

Directional oil wells provide larger pay-zone (extraction zone) than the conventional vertical wells; they are therefore considered to be more economical means for oil extraction. Customarily, perforated steel pipes, called “liners”, are used to stabilize the wells. However, these liners are sensitive to environmental effects (i.e., combined high temperature and aqueous or acidic media), and are susceptible to stress corrosion. Perforated glass fiber reinforced polymer (GFRP) liners have been suggested as an alternative to the perforated steel liners to increase the service life of these liners, thereby offering overall economic benefits. In general, however, the mechanical properties of composites are weakened when exposed to such environmental parameters for a long period of time; therefore, the durability of GFRP liners is of concern. In addition, application of externally applied loads could also change the free volume fraction of the GFRP’s matrix; hence, negatively affect its absorption process and diffusion coefficient. The main purpose of this thesis is therefore to investigate the effect of perforation size on the mechanical response of GFRP tubes/liners subject to hostile environments, as well as developing an effective model for predicting the post-exposure mechanical properties and residual life of the GFRP. For that, the long-term performance of four groups of perforated GFRP plates and tubes (with 5, 8 and 11 mm dia. perforations) were experimentally investigated. The first group of specimens was aged in water, while the second group was subjected to externally applied load while being aged in water. The third and fourth groups underwent a similar regime, but aging was done in 15% sulfuric acid solution instead of water. All experiments were conducted at 60 oC. The flexural properties of the specimens were evaluated by three-point bending tests during and upon completion of the saturation process. The observed saturation behaviors were then compared to that predicted using the Fickian and non-Fickian solutions. Furthermore, scanning electron microscopy was used to observe the microstructural changes. Finally, models were developed to predict GFRP’s mechanical properties degradation, as well as its life cycle.