Abnormal gelation phenomenon of Class G oil well cement incorporating polycarboxylic additives and its countermeasures

Self Cite

The class G oil well cement is a type of special cement that can be subjected to a high temperature formation environment. It was found that the class G cement tail slurry with a low polycarboxylic retarder dosage (usually ≤1% by weight of cement) was more prone to cause the abnormal gelation phenomenon (AGP) than the lead slurry with a high retarder dosage at a high temperature (usually when T ≥ 120 °C). This study aimed at the occurrence mechanism of this unfavorable phenomenon that seriously endangers the cementing security. Results showed that the abnormal gelatinous region underwent premature hydration; namely, the calcium hydroxide and calcium silicate hydrate (C−S−H) content were all higher than the nongelatinous region, while the copolymer content was the opposite. Correspondingly, the theory of "premature hydration and crystal nucleation" was proposed to explain the abnormal gelation mechanism of a cementing tail slurry with an insufficient retarder dosage. Furthermore, a novel functionalized copolymer retarder "PAIANS" was synthesized to alleviate the AGP.

Section: Occurrence Mechanism Of Agpmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Occurrence Mechanism of the Abnormal Gelation Phenomenon of High Temperature Cementing Slurry Induced by a Polycarboxylic Retarder

Xia,

Zhang,

et al. 2024

Self Cite

“…Even slight fluctuations of the concentration would lead to significant differences in the thickening time, which are not conducive to formulation debugging and safe construction. In particular, although few cement retarders show satisfying temperature resistance and long-lasting retarding properties, thickening mutations would appear at 110 to 130 °C; several or even dozens of Bc “bulging” and “stepping” are generated in the silicate oil well. − As the existing study reported, polymeric retarders might overcome the above insufficient conventional retarders. However, most research on polymeric retarders has focused on the adjustment of the functional group and molecular weight.…”

Section: Introductionmentioning

confidence: 98%

Synthesis and Evaluation of Highly Inhibitory Oil Well Cement Retarders with Branched-Chain Structures

Lv,

Zhang,

Xie

et al. 2023

Self Cite

Cementing at medium temperature and high temperature (90–150 °C) is facing challenges on account of the properties of the retarders. Except for the thermal stability, abnormal gelation, such as “bulging” and “stepping”, often takes place and results in safety problems. In this article, the synthesis of a new retarder DRH-150 was introduced. First, a main chain with thermal-resistant groups, 2-acrylamido-2-methylpropanesulfonic acid-acrylic acid (AMPS-IA-AA) was prepared by free radical polymerization. Second, the retarder with a branched structure was synthesized by the grafting reaction. Evaluation of the construction performance showed that, within the temperature range from 90 to 150 °C, the initial viscosity of the cement slurry with DRH-150 was less than 15 Bc, exhibiting an adjustable thickening time and a dosage sensitivity of less than 20%. Meanwhile, no abnormal gelation phenomenon was observed. Referring to the static gelation, both the transition time and the starting strength time (1 MPa) were short. The overall results proved that the retarder DRH-150 might ensure the safety of well cementing and improve the wellbore sealing effect in deep wells, ultradeep wells, and complex wells.

“…The process of oil and gas well cementing operation is to insert a casing into the oil and gas well after drilling the oil and gas well hole and filling the cement slurry between the casing and the well wall. 15 The oil and gas well cementing operation is aimed at sealing the stratum of different pressures by pumping cement slurry into the annulus between the casing and the stratum to prevent fluids in the high-pressure stratum from flowing into the low-pressure stratum through the well bore. The drilling fluid used in the drilling process contains much bentonite; after the oil and gas well cementing operation, a mud cake with a thickness of 2−5 mm often exists between the cement sheath and the wall of the oil well, wherein, the primary component of the mud cake is bentonite.…”

Section: Introductionmentioning

confidence: 99%

“…This paper proposes a novel application of hydrogels in improving the sealing of cement sheath in oil and gas wells. The process of oil and gas well cementing operation is to insert a casing into the oil and gas well after drilling the oil and gas well hole and filling the cement slurry between the casing and the well wall . The oil and gas well cementing operation is aimed at sealing the stratum of different pressures by pumping cement slurry into the annulus between the casing and the stratum to prevent fluids in the high-pressure stratum from flowing into the low-pressure stratum through the well bore.…”

Section: Introductionmentioning

confidence: 99%

Bentonite–Acrylamide Hydrogels Prepared by the Nonmixing Method: Characterization and Properties

Guo

Yang

Wang³

et al. 2019

A significant amount of research has been conducted on bentonite–acrylamide hydrogels. These gels are usually prepared by uniformly mixing bentonite with reactive monomers. Herein, a new preparation method of bentonite–acrylamide hydrogels has been proposed to cater to one novel application of bentonite–acrylamide hydrogels. In this method, bentonite–acrylamide hydrogel was obtained by pressing bentonite into a thin mud cake and extruding a mixed liquor of acrylamide, a cross-linking agent, an initiator, and water into the thin mud cake and then subjecting the system to water-bath curing. The effects of extrusion pressure, extrusion time, and acrylamide concentration on the tensile strength and elemental composition of bentonite–acrylamide hydrogel were investigated. The results show that the tensile strength of the bentonite–acrylamide hydrogel first increased and then tended to be stable with the further increase in extrusion pressure and extrusion time. As the concentration of acrylamide increased, the tensile strength of the bentonite–acrylamide hydrogel increased first and then decreased slightly. With the increase in extrusion pressure, extrusion time, and acrylamide concentration, the contents of C and N elements in the thin mud cake gradually increased and then tended to be stable, which reflects the state of the monomer entering the thin mud cake. In addition, the elemental composition of the bentonite–acrylamide hydrogel was analyzed via the scanning electron microscopy–energy dispersive X-ray spectrometry method, and it was found that the composition of the hydrogel was relatively uniform in the direction of mixed liquor extrusion.