Research Progress and Development Suggestion of Stratified Acidizing Strings in Water Injection Wells of Shengli Oilfield

Stratified acidification is an important technique to solve the problem of the heterogeneity along the borehole and the blockage in the injection wells in Shengli Oilfield, which can be implemented by means of stratified acidizing strings. The technical requirements for this technique were analyzed and its current research situation was summarized with the field practice of Shengli Oilfield. According to the analysis, the existing basic strings, namely the K344, Y211/Y221, and Y341 could meet the requirements of the stratified acidizing of common injection wells in integrated, fault-block, and low-permeability reservoirs in Shengli Oilfield. In addition, some specialized strings were developed to realize pickling (acid-replaceable stratified acidizing strings), integrated acidizing and efficient flowback (acidizing-flowback integrated strings), integrated stratified acidizing and separate water injection (stratified acidizing-separate injection integrated strings), as well as the re-acidizing of a single layer (re-acidizing completion strings). Although these techniques have been widely adopted in the field with satisfied results, they are still far from meeting all the field requirements and the demands for lower cost and higher efficiency. Regarding these shortcomings, some suggestions were put forward including continuous optimization of stratified acidizing strings, further research on multi-functional integrated strings, and deeper studies of intelligent injection techniques and smart strings.