Advanced Light Weight Thixotropic Lost Circulation Cement Solution for Vugular and Natural Fractured Limestone Formations: UAE Offshore Case History

Lost circulation while drilling across vugular or naturally fractured limestone formations is a costly challenge and has financial impacts including nonproductive time and remedial operational expenses. Many fields in the UAE are encountering notorious lost circulation complications, which are difficult to control with conventional lost circulation solutions while drilling surface sections. Novel lightweight thixotropic cement has proven beneficial to take control of severe losses in these vugular and naturally fractured limestone formations. The main challenge while drilling across the surface section in UAE offshore field is the heavy or total loss of returns. Drilling performance is affected due to poor hole cleaning, a risk of stuck pipe, surface fluid handling problems, and well control risks. Conventional extended cement slurries have been widely used to cure losses while drilling but with limited success. A new lost circulation solution combines lightweight (10.5- lbm/galUS) high solids fraction cement (trimodal system) and a thixotropic agent, which develop fast gels with high compressive strength. Thus, it enables plugging of large voids and fractures to deliver the wellbore integrity required to continue drilling with enhanced performance and efficiency. Intensive laboratory qualification tests focusing on static gel strength and compressive strength development was performed to tailor the new solution. The results were promising with more than 100 lbf/100 ft2 of static gel strength in 10 minutes and compressive strength development of 1,000 psi within 24 hours at low surface temperature. In addition, a transition time (TT) on-off-on test demonstrated more rapid gel strength development when the shear is reduced and regained fluidity with reapplication of shear. In one of the wells, heavy losses were encountered while drilling across surface section. The lightweight thixotropic solution was pumped for the first time worldwide and it was shown that the innovative lost circulation solution was effective in significantly reducing the losses and enabled the operator to continue drilling to section TD. This case study demonstrates that this advanced system is effective in curing losses and reducing nonproductive time. The unique properties of faster rapid gel strength and high compressive strength make this solution effective for treating a wide range of lost circulation events while drilling. Furthermore, the advanced lightweight thixotropic cement lost circulation solution exhibits strong performance in curing heavy losses and establishing well integrity with reliability.

Facile and Controllable Preparation of poly(St-co-MMA)/FA Microspheres Used as Ultra-Lightweight Proppants

Hydraulic fracturing is an important technology for the exploitation of unconventional oil or gas reservoirs. In order to increase the production of oil or gas, ultra-lightweight proppants with a high compressive strength are highly desirable in hydraulic fracture systems. In this work, a new type of ultra-lightweight proppant, poly(styrene-co-methyl methacrylate)/fly ash (poly(St-co-MMA)/FA) composites with a high compressive strength were prepared via in situ suspension polymerization. The Fourier transform infrared (IR) and X-ray powder diffraction (XRD) analyses confirmed that the poly(St-co-MMA)/FA composites were successfully prepared. The morphology analysis indicated that the composite microspheres show good sphericity, and FA powder was evenly dispersed in the matrix. The apparent density of the microspheres was between 1 and 1.3 g/cm3, which is suitable for hydraulic fracturing. Furthermore, the compressive strength and thermostability were dramatically improved with the incorporation of FA, which could withstand high pressures and temperatures underground. The obtained poly(St-co-MMA)/FA composite microspheres are promising for application as an ultra-lightweight (ULW) proppant in oil or gas exploitation, which provides a new approach for the design of high performance proppants.

Waste-Based One-Part Alkali Activated Materials

Ordinary Portland Cement is the most widely used binder in the construction sector; however, a very high carbon footprint is associated with its production process. Consequently, more sustainable alternative construction materials are being investigated, namely, one-part alkali activated materials (AAMs). In this work, waste-based one-part AAMs binders were developed using only a blast furnace slag, as the solid precursor, and sodium metasilicate, as the solid activator. For the first time, mortars in which the commercial sand was replaced by two exhausted sands from biomass boilers (CA and CT) were developed. Firstly, the characterization of the slag and sands (aggregates) was performed. After, the AAMs fresh and hardened state properties were evaluated, being the characterization complemented by FTIR and microstructural analysis. The binder and the mortars prepared with commercial sand presented high compressive strength values after 28 days of curing-56 MPa and 79 MPa, respectively. The mortars developed with exhausted sands exhibit outstanding compressive strength values, 86 and 70 MPa for CT and CA, respectively, and the other material’s properties were not affected. Consequently, this work proved that high compressive strength waste-based one-part AAMs mortars can be produced and that it is feasible to use another waste as aggregate in the mortar’s formulations: the exhausted sands from biomass boilers.

Comparative Analysis Between Fly Ash Geopolymer and Reactive Ultra-Fine Fly Ash Geopolymer

This study investigates novel geopolymers by combining Reactive Ultra-fine Fly Ash (RUFA) with 4M sodium hydroxide as an alkali activator. Comparing with general fly ash geopolymers, RUFA geopolymer pastes are characterized in terms of compressive strength, microstructure, and crystalline phases. The RUFA geopolymer is successfully obtained as alumina-silicate bonding materials with the same properties as the general fly ash-based geopolymer. The high compressive strength of the RUFA-based geopolymer samples (13.33 MPa) can be attributed primarily to Ca-based alumino-silicate hydration products and Na-based alumino-silicate complexes. This research presents an innovative application for geopolymers using RUFA. In the follow-up study, the influence of synthesis and concentration of alkali activator can be considered in RUFA-based geopolymers.

The Relation Tensile Strength And Flexibility Of Bamboo For Soil Stabilization

Bamboo is an abundant material and easily available in Indonesia. In addition to having high compressive strength and tensile strength as well as ease of obtaining and low prices, bamboo is a consideration and focus in developing in the world of construction today. In this study, bamboo is used for soil stabilization, where bamboo is used in the form of fibre. This research focuses on the strength properties of various types of bamboo. The focus is to investigate the relationship between the maximum tensile strength of bamboo and the flexibility of bamboo in soil stabilization. This is very important, because bamboo fibers used for soil stabilization rely on their tensile strength rather than their compressive strength. Thus, the optimum tensile strength and flexibility of bamboo must be of particular concern. From the results of the study of the tensile strength of two types of bamboo, namely Apus Bamboo and Java Bamboo, the Apus Bamboo results were found to have a higher tensile strength of 225.57 mpa with maximum flexibility of 19.99 mm and 43.76 mpa for tensile strength of Javanese Bamboo with a level of flexibility of 10.26 mm.

Effect of Casting Temperatures and Curing Methods on Concrete Properties

This study concentrates on the effects of curing methods and casting temperatures on concrete properties in cases of fresh and solid states. The targeted strength of the concrete mix is 25 N/mm2. An experimental work was performed at the laboratory of the Faculty of Engineering, University of Khartoum. Initially the tests on the basic materials (cement, fine aggregate, coarse aggregate) used. The program was testing the strength of concrete for a number of 80 samples of three cubes and test for absorption of water for 16 samples. These samples were casted at temperatures of 15, 25, 35 and 50 c0 and cured with four different methods. Methods of curing used are immersing the samples in water, cured through the winding sample with Hessian and sprinkled water, winding samples with plastic sheets to prevent evaporation of water or loss of water from the sample and paint samples with doofagard. In addition some samples were uncured. The samples were broken in three days, seven days, 28 days and 56 days. In the water absorption tests the samples were casted at different temperatures and different methods of curing except a coating sample with doofagard because the sample cannot absorption water. Also the workability tests for the samples casted at temperatures 15, 25, 35 and 50 c0 were performed. The find out of these experimental works showed that: (1) the compressive strength of cement concrete specimens increased with the period of curing (2) curing of concrete by immersion in water results in a high compressive strength than the other methods of curing (3) The concrete will gain low compressive strength if it is not cured at all after casting (4) The best degree of casting temperatures is 15 and 25 c0 that resulted in a good workability and high compressive strength; on the other hand casting concrete at high temperature reduce workability of fresh concrete.