One of the challenges when drilling, especially in a HPHT(High Pressure High Temperature) environment [1], is the well integrity as far as the cement is concerned. It is well known that cement has a tendency to degrade in corrosive environment and high temperatures. Due to chemical attacks and formation movements and the consequent mechanical failure that was experienced in many cases many oil and gas companies decided to search for potential material for oil well cementing operations [2]–[5] . Alumino-silicates that are industrial waste and powdered residue from the combustion of coal having pozzolanic properties such as fly ash [6] and have geopolymerization potential have attracted scientific attention the last 10 years. In order to have a positive environmental impact combined with the use of a new material, it is important to seek materials that are in abundance locally. The current project aims at identifying any viable combinations of waste/residues that can result in a binder capable of withstanding chemical attacks and high temperatures while being strong enough to sustain formation stresses. In Denmark fly ash from power plants is an inexpensive source of aluminosilicates. There are two ways to produce cement/binder from aluminosilicate source. The oldest and most conventional (zeolitic method) is user-hostile while the user-friendly (geopolymerization) method yields less Uniaxial Compressive Strength (U.C.S.) [7]. The safety of the end-user is of utmost importance and the U.C.S. values do not give the actual point of failure of the placed cement [8]. Therefore, both methods were tested and a hybrid one too. For the geopolymerization method, an additional material is needed (electric arc furnace slag-EAFS was chosen over the frequently tested Ground Granulated Blast Furnace slag) that is not locally abundant (in Denmark) but is rather inexpensive and transportable through neighboring countries e.g. Germany. The main use of the new binder under test is oil well cementing applications. However, in order for a new product to be commercialized and achieve industrial acceptance must have characteristics that extend beyond the boundaries of oil industry. The Ordinary Portland Cement(OPC) with the addition of certain reagents can be applied in areas ranging from tunnel construction to oil well cementing operations. An OPC alternative must have the same versatility. One basic advantage that is widely recognized is the lower CO2 footprint (compared to OPC) of the geopolymerized/alkalinated binder manufacture [9]–[16]. Ultimately, the new binder must achieve similar performance in popular OPC applications (if not better).
At Chapter 1 a literature review is provided so the reader would get accustomed to the terminology regarding cementing operations, history, process and the potential of geopolymerization method (and the conventional method too). A brief introduction of the application of cement in oil wells in also provided.
Chapter 2 is dedicated to experimental procedures (materials, mix designs, preparation, test methods and test analysis).
The experimental results are the topic of the Chapter 3 where the properties of the binder, Uniaxial Compressive Strength (U.C.S.) tests, pH and rheology measurements, penetrometer tests, durability tests, Differential Scanning Calorimetry measurements and X-Ray Diffractometry analysis are presented.
Next, at Chapter 4 discussion of the results presented is done where the effects of some test parameters e.g. curing temperature is analysed.
Finally, Chapter 5 concludes the current study with the reached conclusions and some topics for further/future investigation.