Study On Mechanism Of Network Structure Of Cementation At Cement-Formation Interface

Extraction of petroleum and natural gas is a complex process. It needs to solve the problems of exploration%drilling、well completion、cementing、fracturing、water injection、production and so on in need to be solved the process. Through With the scientific research and experience accumulation on solving practical engineering problems, and various new petroleum technologies has been being widely applied and matured. But, there are still several urgent technical problems need to be solved including fluid channeling in annulus after cementing, which directly affect oil and gas output and the production capacity for oil-gas wells, such as fluid channeling in annulus after cementing. The quality of one well cementing not only directly affect drilling and completion, but also affect subsequent production of oil and gas development, oil recovery, working life of wells, etc. So if fluid channeling in annulus after cementing happens, it will make effect of cementing difficult to embody, drilling and production work unable to proceed, what’s more, it will and even make the well abandonment..According to the dates, about25%oil-gas wells had different degree of fluid channeling in annulus after cementing all over the world with huge losses. In china, many oil fields have been flooded by water for several years. With energy demand increasing, oil and gas development in difficult reservoirs is imperative. So the fluid problem of channeling in annulus after cementing initiated by high-pressure fluid operation such as acid fracturing become more serious. And a lot of scholars at home and abroad have recognized that the isolation system invalidation of cement-formation interface is the main cause of fluid channeling in annulus.Because of the complexity of cementing environment, it is difficult for pure cement slurry to meet the demand of cementing operation to ensure cementing processes and cementing quality. Commonly, shaft lining need to be treated or a proper quantity of chemical reagent need to be added into cement slurry to improve the compatibility of cement-formation interface and cementing quality. As cementing materials, polymers are widely used and play a great role in cementing operation. This paper deeply study the characteristics、application effect and mechanism of a new polymer pad fluid, and described the formation process and significance of cementation network structure on cement-formation interface. It opened out the mechanism of cementation network structure improving the interfacial properties of cement slurry-cake, modifying the two-phase joint surface, promoting ionic exchange, producing new minerals and increasing cementing strength. What’s more, it analyzed the synergistic effect process of cementation network structure and various active components on microcosmic angle relying on test method such as TG\XRD\IR\SEM\XPS and so on. It seek the deep influence mechanism of cementation network structure increasing cementing strength, elaborate the effect process and model of cementation network structure, summarize the existing sate and effect mode of action of various active components in cement-formation interface, provide theory basis and guidance for project practice. To sum up, it obtains the following main results:1. According to simulate the field cementing process and conditions, we have formed the cementation network structure in cement-formation interface, and studied the application effect and change law of the cementation network structure to increasecementing strength. The results showed that the cementation network structure make cementing strength of cement-formation interface formed cementation network structure are uniform stable and increased three times with stable and obviously increasing.2. Composition was tested by multiple modern measurement technology to study the changes and reactions of cement-formation interface from microcosmic angle. The results shows that:(1) Contents of O, Na、Mg、Al、Si、K、Ca, Fe and some other elements increased significantly under the action of cementation network structure in cement-formation interface. And most of these change from silent state into active state.(2) Under the action of cementation network structure, many minerals in various forms and structure with cementitious behavior and high strength in are appeared in cement-formation interface.(3) The SEM test show that:under the action of cementation network structure, cementation network structure were formed in cement-formation interface. A part of this structure connected with cake, the other part combined with cement paste. The minerals in cement paste and cake interpenetrated, formed a whole pattern. This structure makes the boundary of cement paste and cake fuzzy and promote integrated cementation3. This article study The formation process and structural characteristics of cementation network structure in cement-formation interface, and described effect process and model of cementation network structure.(1) GJ-II cake curing agent makes the ingredient of inorganic minerals in mud cake occur depolymerization reaction and appear broken bond of metal ions, produce raw material for subsequent reaction.(2) By Generating metal chelates, hydrogen bonds, non-qualitative adsorption,anion exchange and polymer-cation intercalation complexes, etc, GJ-I cake curing agent combined with the scattered cake mineral and cement paste.(3) Active substances were adsorbed on the GJ-I cake curing agent surface, and generated high-strength minerals such as hydrated calcium silicate, calcium carbonate and so on. Then cementation network structure has been formed. The minerals on surface of cementation network structure provided high strength, and the polymer in inner core of cementation network structure provided high toughness. 4. The network structure has an effect on the phase and structure in cement-formation interface. It describes synergistic effect of the structure and plaster, ferric hydroxide, high aluminium gelmaterial and so on, which enhance the mode of action of cement-formation interface’s bond strength.5. During the studying of the forming of network structure of interface cementation and synergistic effect with related components, we discover that-OH and COO-etc. are the mainly utility group in polymer pad fluid. These groups interacted with the minerals in mud cake and cement paste, improved the extent of the curing reaction, produced new minerals with cementitious behavior and high strength, and then increased cementing strength.