The Potential of Using Cr3+/Salt-Tolerant Polymer Gel for Well Workover in Low-Temperature Reservoir: Laboratory Investigation and Pilot Test

Abstract

Summary Using mature Cr3+/partially hydrolyzed polyacrylamide (HPAM) gel can reduce filtration for water shutoff in the fractured reservoir. Whether the mature gel can act as a fluid-loss-control pill for well-workover operation is worth investigating. In this paper, we start a systematic experimental study to reveal the physical process and fluid-loss-control mechanism of the Cr3+/KYPAM (salt-tolerant polymer) gel used for overbalanced well workover. The polymer gel used in this study is formulated with a combination of 0.4 to 0.6 wt% KYPAM and added 0.02 to 0.04 wt% chromium acetate, which can provide a gelation time between 2 and 4 hours, and with a maximum gel strength of Code G at a temperature of 30°C. Results show that the mature Cr3+/KYPAM gel can withstand positive pressure of 10 MPa for a period of 120 minutes with average fluid-loss volume of 15 cm3 for the core permeability between 9.18 and 217 md, indicating a favorable fluid-loss-control performance. The regained-permeability recovery can reach up to 85% for different core permeabilities. Scanning-electron-microscope (SEM) pictures show that a dense structure was formed in the gel filter cake during fluid-loss experiment. The wettability results show that the core has a greater potential to increase its water-wet ability after interacting with Cr3+/KYPAM mature gel. Field test shows that a small amount of gel leakoff was observed during each reperforation process, whereas water cut decreased from 89.1 to 52.1% and oil production increased from 0.15 to 1.11 m3/d. This study suggests that the mature Cr3+/KYPAM gel can act as a fluid-loss-control pill in high-water-cut oil wells, which can provide an avenue to bridge the design philosophy of well workover and water shutoff.

The Thermal Gelation Behavior and Performance Evaluation of High Molecular Weight Nonionic Polyacrylamide and Polyethyleneimine Mixtures for In-Depth Water Control in Mature Oilfields

“…The hydrolyzed polyacrylamide contains many amide groups (-CONH 2 ) and carboxyl groups (-COO − ) in its molecular chain. It could crosslink with different types of crosslinkers, such as Cr 3+ [ 6 , 7 ], Al 3+ [ 8 ], Zr 4+ [ 9 ], phenolic resin [ 10 , 11 ], etc. However, multivalent metal ions and phenolic resin are toxic.…”

The Thermal Gelation Behavior and Performance Evaluation of High Molecular Weight Nonionic Polyacrylamide and Polyethyleneimine Mixtures for Indepth Water Control in Mature Oilfields

“…The polyacrylamide contains a large number of amide groups (-CONH2) and carboxyl groups (-COO -) in its molecular chain after hydrolysis. It could crosslink with different types of crosslinkers, such as Cr 3+ [6,7], Al 3+ [8], Zr 4+ [9] or phenolic resin [10][11] et al. However, multivalent metal ions and phenolic resin are toxic.…”

Effect of carboxylic group on the compatibility with retarder and the retarding side effect of the fluid loss control additive used in oil well cement

“…Normally, well cementing requires placement of the casing pipe into the well to a specified depth, and then pumping cement slurry into the annular space between the casing and formation through the casing. During well workover, filtration will occur when cement slurry is placed in contact with a permeable formation [ 5 – 7 ]. During application of the cement slurry, the aqueous phase of the slurry escapes into the formation, leaving the cement particles behind.…”