Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Study on strengthening fluid for the weakly consolidated shallow formation in deep-water: effectivefactors and curing effect
Leiju TIAN a, Yuhuan BU a,*a School of Petroleum Engineering, China University of Petroleum.
Qingdao, Shandong Province, China.

mechanical properties of the two materials is a challenge even for theelastic cement slurry system (LIU et al., 2016; Diarra, R., 2017; Pang,X,2017; WANG et al., 2019). Therefore, we propose a novel
strengthening fluid that reinforces the weakly consolidated formation toeliminate or reduce the sudden change in mechanical properties between
the formation and cement sheath. The strengthening fluid is water-borne
epoxy resin-based and can penetrate the weakly consolidated shallow
formation and reinforce it. In this way, the cement sheath and formation
can consolidate as an entirety. Due to the pore of shallow formationbeing full of seawater (LIU et al., 2016; Tian et al.), it is inevitable toblend seawater during the penetration of the strengthening fluid into theformation. Furthermore, alkaline filtrate will also loss when cement
slurry sets (DU et al., 2019; CAO et al., 2021). Those fluids may
influence the curing of strengthening fluid.

ABSTRACTThe mechanical properties of weakly consolidated shallow formation are
low strength and low Young's modulus while the Portland cement is highstrength and high Young's modulus. The cement sheath can easily
undergo brittle failure under this condition, which is severely threatening
the cementing isolation quality of oil and gas wells. Bridging the huge
difference in the mechanical properties of the two materials is achallenge even for the elastic cement slurry system. Waterborne epoxy
resin was applied as a strengthening fluid for the weakly consolidated
shallow formation in deep-water to improve the cementing quality. An
artificial core was utilized to evaluate the reinforcing effect. The resultshows that the blended formation fluid can increase the compressive
strength of the curing product with a dosage of less than 40 %. The
control group indicated that the inorganic salt in the formation water isbeneficial for the reinforcement of the formation. The evaluation
experiment indicated that the strengthening fluid can significantly
increase the cement-formation interface strength.

In this study, the effect of seawater on the strengthening fluid wasevaluated. Second, the effect of the fluid pH on the strengthening liquid
is revealed. Moreover, a kind of simulation core and cement-formation
strength were used to evaluate the reinforcing effect of the strengthening
fluid on the weakly consolidated formation.

KEYWORDS: Deep-water oil and gas well; Well cementing; Weakly
consolidated shallow formation.

EXPERIMENTINTRODUCTION

Materials

The isolation integrity of oil and gas wells is essential for isolating
formation fluids (Mangadlao et al.,2015; Liu H. et al.,2016). Accidents
caused by cement sheath failure are often severe threaten the marine
ecology (Liu, Z.et al., 2015) and are costly to resolve, especially in theocean (Pan et al., 2015; WU et al., 2018).

The materials and additives applied in this work are list in Table 1. The
basic performance of ER used in this work are: colorless; epoxy
equivalent 180-190 g/eq; viscosity 12 000-14 000 mPa·s at 25 ℃;
internal code NPEL-128.

The principal components of weakly consolidated shallow formations indeep water are unformed rock silt and sand. In addition, the weakly
consolidated shallow formation in deep water can extend hundreds ofmeters below the mud line (Eoff, 2000; Lavasani, 2011; Skogdalen,2012). In 2010, the wellhead device of Husky Energy's LH29-1-3 wellsunk approximately 2.5 meters, nearly causing the well to scrape. (Liu,2015). The mechanical properties of weakly consolidated shallow
formation are low strength and low Young's modulus while the Portland
cement is high strength and high Young's modulus (Ribeiro, D,2019;
Zhang et al., 2019; DU et al., 2018). The cement sheath is prone to brittle
failure under these conditions, posing a danger to the cementing isolation
quality of oil and gas wells. Bridging the huge difference in theTable 1 Materials and additives applied in this work.
Material
Manufacturer or Provider
Class G oil well cement Jiahua Special Cement Co., LTD.
(OPC)
(China)Epoxy resin (ER)NANYAElectronicMaterials(E-51 type)(Kunshan) Co., LTD.
Metakaolin
Jiaozuo Yukun Mining Co., Ltd. (China)
Curing agent (CA)Shanghai Hanzhong Dope Co., LTD.
Defoamer
SAN NOPCO LTD.
(SN-154)
NaOH (99 % purity) &Sinopharm Chemical Reagent Co., LTD.
Coupling agent, (KH-617