Ahmed S. Al-Humaidi

Investigation of Water-Swelling Packers

Achieving successful zonal isolation during well completion is critical to minimize early water production. Currently, cementing is the only method used in Saudi Arabian fields to provide zonal isolation. In horizontal sections, cementing becomes a challenge and excessive water production 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 article outlines step-by-step qualification testing that was carried out in Saudi Aramco facilities in an attempt to improve zonal isolation in horizontal and multilateral wells. In this study, we present lab evaluation of elastomers at 190 oF 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 weight-percent (wt%) hydrochloric (HCl) acid on the swelled elastomers, and whether or not the exposure to water after the acid exposure will restore their size. To the best of the authors’ knowledge, no previous work was conducted to examine the impact of these factors on water swelling packers. The elastomer bonded in pipes was tested in autoclaves. The pressure drop across the pipe was measured as a function of time. The influences of pH and divalent cations on water swelling packers were investigated using elastomer samples. Swelling was related to fluid characteristics. Some water swelling elastomers withstood pressures up to 5,000 psi at 190 oF after placing the elastomers in brines with salinities up to 200,000 mg/l. The swelled elastomers shrank in 15 wt% HCl. Calcium chloride (CaCl2) completion fluids at 72 pounds per cubic foot (pcf) failed to swell the elastomers. The swelled elastomers shrank in 15 wt% HCl acid and their swelled size was not regained after soaking in water. This article discusses the advantages and limitations of swelling elastomers and gives recommendations for field application.

An Innovative Cement Formula To Prevent Gas-Migration Problems in HT/HP Wells

Gas Migration through cement columns has been an industry problem for many years. The most problematic areas for gas migrations are 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, gas can leave the reservoir and 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 increase in permeability. To solve the settling problem and reduce permeability, Saudi ARAMCO had developed a formula that resulted in great gas prevention. A gas migration model helped in testing and optimizing cement formulations to measure gas flow through cement columns. The gas migration model consists of the following systems: 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 were investigated. In this paper, a new cement system was developed and results in great gas prevention. The performance of this system outstand any known existing gas cement formulations and has great potential to improve wellbore isolation in gas wells in Saudi Arabia.

Swelling Packers: Lab Testing and Field Application

The 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.