Gas Migration through cement columns has been an industry problem for many years. The most problematic areas for gas migrations occur in deep gas wells. To control gas migration, cement densities required to successfully cement the zone could be as high as 170 pcf (Pounds per Cubic Foot). As cement slurry sets, hydrostatic pressure is reduced on the formation. During this transition, reservoir gases can travel up through the cement column resulting in gas being present at the surface. The permeable channels, from which gas flows, cause operational and safety problems at the well site.Current high density cement formulations do not provide good gas migration prevention due to settling and subsequent increase in permeability. To address the settling problem and reduce permeability of cement, a formula that resulted in great gas prevention was developed.A gas migration set-up helped in testing and optimizing cement formulations to measure gas flow through cement columns. The gas migration set up consisted of the following components: computer, data acquisition, full-length permeability determination, two partial length permeability determinations, cement volume change measurement, gas flow meter, and electronic filtrate weight determination. The pressure and temperature limitations are 2,000 psi maximum and 350°F. Different chemicals for gas migration prevention were evaluated. Special types of cements were designed and evaluated for possible use for cementing gas wells. Addition of inert particles to cement and their effect on gas migration prevention was investigated.In this paper, a new cement system was developed and resulted in significant gas prevention. The performance of this system outperforms available formulations and has great potential to improve wellbore isolation in deep gas wells.

Achieving successful zonal isolation during well completion is critical to minimize early water production. Currently, cementing is the only method used in Saudi fields to provide zonal isolation. However, in horizontal sections, cementing becomes a challenge and water flows can occur due to channeling. Another method for zonal isolation is to use a rubber elastomer bonded onto a base pipe. The rubber swells in water and provides a seal between the base pipe and the open hole. This paper will outline the step-by-step qualification testing that was carried out in Saudi Aramco facilities in an attempt to improve zonal isolation in horizontal and multilaterals wells. In this study, we present lab evaluation of elastomers at 190ºF using brines of different ionic strengths and pH values. The evaluation involved examining the effect of salinity and pH on the rate of swelling of elastomers. Also, the study investigated the effect of 15 wt% HCl acid on the swelled elastomers. To the best of the authors' knowledge, no previous work was done to examine the impact of these factors on the swelling mechanisms. The elastomer bonded in pipes was tested in autoclaves. The pressure drop across the pipes was measured as a function of time. The influences of fluid density and viscosity were also investigated using elastomer samples. Swelling was related to volume of the samples and fluid characterstics. Water swelling elastomers withstand pressures up to 5,000 psi at 190ºF after placing the elastomers in salinities up to 200,000 mg/l. However, the swelled elastomers shrink in 15 wt% HCl. This paper discusses the advantages and limitations of swelling elastomers and gives recommendations for successful field applications. Introduction Swelling packers can be used for multiple-zone open-hole completions. These packers will swell when they come in contact with wellbore fluids (either crude oil or water). Open-hole completions become attractive because they require fewer trips and no cementing near-wellbore which can cause formation damage. Swelling packers can be used for any of the following reasons:1 Horizontal sections where cementing is difficult, lateral zones with compartmental isolation, and zones with large permeability variations. There are no operational difficulties in running the swelling packers. There are two types of packers; water-swelling and oil-swelling. Contaminations in the wellbore fluids can affect the swelling of the packers. Oil swelling elastomer will swell faster in lighter oils compared to heavier ones. In field applications where acid stimulation is required, the swelling packers will be exposed to acids. Hydrochloric acid is commonly used to matrix acid carbonate formations. Concentrated HCl acids will affect the swelled packers, but not the weak ones.1 Swelling of oil packers depend on thermodynamic absorption process. All liquids have a solubility parameter, which is the energy required to vaporize them. The packers have two components; a polymer and a flexible material. When the polymer is immersed into a liquid with a similar solubility parameter, a strong affinity between the polymer and liquid will cause swelling of the polymer and, as a result, the flexible material will expand and the volume of the packer will increase by several folds. 2 Swelling will continue until equilibrium is reached. The time to reach equilibrium will be reduced at higher temperatures. When swelling reaches equilibrium, the mechanical properties and volume of the packer remain constant. If further expansion is reached, it will be due to thermal chain degradation of the polymer. When expansion is limited by the wall of the hole, the packer will not reach equilibrium and will continue to swell until it does.2

Achieving successful zonal isolation is critical to install smart completion tools. Currently, cementing and mechanical packers are the only conventional methods used in Saudi fields to provide zonal isolation. However, these techniques are difficult to operate and result in reduced inner casing string diameter. Another method to provide zonal isolation for smart completion tools and to complete them in single stage is to use a rubber elastomer bonded onto a base pipe. The rubber swells in oil and provides a seal between the base pipe and the open hole. This paper will outline the step-by-step qualification testing that was carried out by Saudi Aramco facilities in an attempt to improve zonal isolation for smart completions.In this study, we present lab evaluation of elastomers at 190°F using six different oil samples. The evaluation involved studying the effect of oil viscosity and API gravity. Also, the study investigated the effect of acids on the swelled elastomers. To the best of the authors' knowledge no previous work was done to investigate the impact of these factors on the swelling mechanisms.The elastomer bonded in pipes was tested in autoclaves. The pressure drop across the pipes was measured as a function of time. The effects of other factors were investigated using elastomer samples and fluid characterization. The oil swelling elastomers withstood pressure up to 5,000 psi at 190°F after placing the elastomers in some crude oils. In addition, the elastomers swelled rapidly in some oils and slowly in others.

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TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractThe best well completion is the lowest cost one that meets the demands for the well during its life time. There are different aspects that we need to consider when designing completion such as reservoir consideration (Allen and Roberts, 2006).We can have openhole completions, perforated casing completion, or horizontal completions. In this study, we present lab evaluation of oil and water swelling elastomers for potential field application in Saudi Arabia fields.Oil and water swelling packers were examined in the lab (measuring pressure difference across swelling packers in autoclaves at 190°F and testing against various salinity fluids and pH using coupons at 190°F). Crude oils with various properties were used to test the oil swelling packers. Water swelling packers were tested in aqueous fluids with various pH values and salinities.Oil swelling packers showed acceptable pressure drops across the packer for six crude oils. They were resistance against acids and different brines. Oil swelled elastomers were tested with different salinity fluids to simulate the effect of produced water on the oil swelling packers. They were also tested against various acids to simulate possible stimulation treatments. The water swelling packers showed acceptable results for all fluids tested except at high and low pH fluids. This limits their use in wells with potential acid treatments.Oil swelling packers were used successfully in 16 oil producers. Cost saving on the rig time was achieved with swelling packers to cased-hole completions. Up to 22% of the rig time was saved due to the elimination of running casing, cementing, using whipstock and casing milling. To date, all wells completed with oil swelling packers are showing good results for close to three years.