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

A New Thermo Sensitive Plugging Spacer and Foam Cement Slurry for the Leakage Formation inShunbei Oil and Gas Field
YUAN GAO, GUANGGUO YANG, SHIMING ZHOU, YONGTAO CHU, JINGNAN XIAOSINOPEC Research Institute of Petroleum Engineering
Beijing, China

the ground successfully, and the cementing quality was excellent. Thistechnology can provide a reference for the leakage-proof cementing job
of fractured formations in other blocks.

ABSTRACTThe fractures in Permian stratum of Shunbei oil and gas field are welldeveloped, the formation fracture pressure is low, and the leakage
problem is very severe during the cementing jobs. It is difficult to solve
this problem by using traditional low-density cement slurry and staged
cementing process techniques. To solve this problem, a new type ofthermo-sensitive plugging spacer and foam cement slurry weredeveloped, and the cementing operation without leakage wassuccessfully realized. The thermo-sensitive plugging spacer isdeveloped based on the principle of “bridging-grading”, consisting ofthermo-sensitive memory expandable mesh, thermo-sensitive memory
expandable pellet, rigid supporting particles, organic fibers andinorganic fibers, which the thermos-sensitive memory expandable meshand thermo-sensitive memory expandable pellet can expand several
times under downhole high temperature conditions. This thermosensitive plugging spacer system can meet the requirements of 8.5 MPapressure-bearing for a fracture of 3 mm wide and can withstand a hightemperature of 150 ℃.
By developing high performance foaming agent and stabilizing agent,
selecting larger-temperature difference retarder and accelerator, etc., afoamed cement slurry system is developed. The cement slurry density
was adjustable in the range of 1.10 - 1.60 g/cm3, and the API fluid loss
was less than 50mL at 120 ℃. The compressive strength was good andthe comprehensive performance was excellent. To solve the problem oflarge density difference of cement slurry caused by the compressibilityof foam, a cement slurry aerating method was designed based on welldepth, temperature, and pressure. The aeration volume of cement slurry
could be adjusted in a real-time way according to well depth, cementslurry density, and pumping rate, so as to guarantee the uniform densityof foamed cement slurry in the annulus.
Using the developed thermo-sensitive plugging spacer system andfoamed cement slurry system, the leakage-proof cementing process has
been formed for low-pressure leakage-prone formation in Shunbei oiland gas field. This technology has been applied for 2 wells, both thethermo-sensitive plugging spacer and foamed cement slurry returned to

KEY WORDS: plugging spacer; foamed cement slurry; segmented
aeration design; cementing.

INTRODUCTION
Shunbei oil and gas field is a marine carbonate fracture-cavern oil
reservoir in the Northern Shuntuoguole area deployed by Sinopec
Northwest Oilfield. The block geological conditions are complex andseveral fault zones are developed, especially the Permian stratum
developed multi-scale 0.1-1 mm wide fractures. The formation is about
500 m thick on average, having a buried deep of 5000m and formation
leakage pressure of 1.25-1.27 g/cm3 (PanJun, 2018; Dong Xiaohu,2020). The low pressure-bearing capacity of this formation leads toserious leakage in cementing job and insufficient cement return, which
seriously affects the integrity of the entire wellbore and poses a major
hidden danger to the safe production of high-pressure oil and gas wells.
At present, there are mainly two types of low-density cement slurrysystems used for low-pressure leakage-prone Permian stratum, i.e., the1.40-1.50 g/cm3 high-resistance microbead low-density cement slurryor 1.60 g/cm3 fly ash low-density cement slurry. There are mainly two
types of cementing processes: one is to use a staged cementing process
for wells with partial slurry return at wellhead, which adopts lowdensity cement slurry as lead slurry, conventional-density cement slurry
as tail slurry in the first-stage, and adopts low-density cement slurry inthe second-stage. Whereas, for the no-return wells, the positive
injection and reverse squeezing process are adopted. The positive
injection slurry is a low-density cement slurry, and the tail slurry is aconventional density cement slurry. Once the positive injection isfinished and the strength of tail slurry is established, the conventional
density cement slurry shall be squeezed reversely. Although the cement
slurry system and cementing process currently used have reduced thefluid loss to a certain extent, the leakage in Permian cementing is still

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