The objective of this research is to investigate the concentration effect on the rheological properties of different bentonite suspensions. Experiments were performed with different bentonite type and concentrations and the results were evaluated by different rheological models (Bingham plastic, Power law, Sisco, Casson, Herchel Bulkley and Robertson Stiff) describing the flow of non-Newtonian fluids by mathematical equations in terms of shear rate and shear stress.
Most of Egypt's Western Desert reservoirs are characterized to have low permeability and heterogeneous, poor rock quality. In the early development stages only layers with high permeability were produced, while the low-permeability, low-porosity layers were not considered economic. As these high-permeability layers became more mature and declined in production, tight layers became the operator's alternative choice to unlock the enormous amounts of hydrocarbons still present in these rocks and achieve economical production targets from these marginal fields. Hydraulic fracturing technology enabled us to unlock the potential of these challenging layers that were previously considered uneconomical. Hydraulic fracturing is now a common practice, even pushing extremes such as deeper, high-temperature and high-pressure wells in the Western Desert. The incremental production gains from these challenging layers have encouraged operators to invest. Currently, hydraulic fracturing is routinely conducted for all new production and injection wells and is reconsidered for the old wells. Completion practices, candidate selection criteria, perforation and design strategies, and workflows were revised to address these new challenging conditions and reservoir complexities with hydraulic fracturing technology. For example, vertical completions were replaced by horizontal multistage fracturing completions to increase the reservoir contact. State-of-the-art software was used to simplify decisions on fracture initiation points across heterogeneous reservoirs. Different technologies, alternative to conventional perforating, were introduced to enhance the proppant placement, post-fracturing production, and operational efficiency. This paper provides a review of hydraulic fracturing in Egypt's Western Desert. The hydraulic fracturing technique has been used to develop mature fields and challenging formations of Egypt since the early 1990s. More than 1,000 treatments targeting low- to medium- permeability rocks were pumped in Khalda Ridge. Correlation between mechanical properties, reservoir properties, essential fracturing design, completions, and operational parameters were established over time to help other operators that intend to apply hydraulic fracturing to their assets. Case histories are also provided, demonstrating different fracturing techniques for extreme conditions. In this paper we detail the progress related to completion practices and technologies to revive the mature fields of Egypt.
This paper describes the successful combination of different stimulation techniques during the development phase of an offshore field in Congo. A total of four wells were drilled and completed during 2008-10. The target reservoir, the Sendji carbonates, has a total thickness of 150-170 vertical meters with an interlayer of ten meters. It is composed of silty-shaly dolomitic and quarzitic sandstone with interbeds of shale and sand grading to sandstone and silt with dolomitic cement characterized by very poor petrophysical properties. Laboratory testing with cuttings showed that formation is more than eighty percent soluble with fifteen percent hydrochloric acid. The typical well has an average azimuth and inclination of 60 and 350 degrees respectively, in the target reservoir. A good quality cementation job of the casing was required in order to ensure isolation from the aquifer. The well completions are both open and cased hole multistage fracturing completion systems. Selected zones of varying lengths were hydraulically fractured by using proppant / seawater-based borate crosslinker fluid or by using twenty percent delayed, viscoelastic and straight acid. Two wells were stimulated by means of proppant fracturing while the other two by acid fracturing. Due to upper / lower water zones with no bounding beds, it was important to define formation mechanical properties for fracturing designs in order to avoid fracturing into water bearing layers. A Mechanical Earth Model (MEM) was created by using sonic anisotropy measurements, modular dynamic test results, and other common electrical logging data together with drilling parameters. The detailed study of design methodology, different stimulation fluids and operation sequences are described. Particular attention will be given to the comparison of well responses to multi-stage proppant and acid fracturing techniques.
A recent series of tight gas discoveries in the Amin format ion of the greater Fahud area represents some of the most exciting exploration success of this decade in the Sultanate of Oman. The structures have been evaluated as containing very significant amounts of gas locked in a challenging deep and hot environment requiring hydraulic fracture stimulation. Recently, horizontal well trials started taking place in two of the structures aiming for testing efficiency of this type of completion and further evaluation of formation deliverability. Successful completion of horizontal laterals would open new horizons in this challenging environment. Achieving this goal is not possible without thorough evaluation of reservoir conditions followed by completion and stimulation. Horizontal well performance in a tight gas reservoir is largely controlled by the number of hydraulic fractures placed along the lateral and their spacing and conductivity. Designing a reservoir access strategy might not be a trivial task, either, when the well trajectory intersects several productive vertical layers and the reservoir properties are changing laterally. Manual selection of intervals and perforations could be susceptible to mistakes and may be perceived as subjective at times, while also being time and effort consuming. The workflow based on reservoir quality (RQ) and completion quality (CQ) developed in North America for unconventional resources for optimizing completion decisions brings engineering to this process for stage and cluster selection in horizontal sections. This project applies the same reservoir-centric RQ/CQ workflow integrating all available data and creating specific criteria and cutoffs applicable to a specific tight gas field in the Sultanate of Oman.
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