Abstract

Well re-entry necessary to wash/cleanup suspected barites and barium sulfate residues in two wells located onshore Niger Delta, Wells AA & BB drilled and completed to develop a cumulative of over 700 Bscf of gas and 30MMstb of associated condensate reserves at an initial cumulative potential of 240 MMscf/d, producing below par at about 15% planned daily production.

The sand face for these Single String Gas Producers were drilled with 13.8ppg POBM. Post well completion, hookup and initial cleanup, the wells were suspected to have remained suspended with drilling and completion debris also, various HUD's were encountered within completion string.

Previous reentries proved rather unsuccessful for the operator as these wells could not be cleaned up even after using 3 different traditional stimulation fluids pumped in high volumes. As a result of the challenges experienced during the previous interventions, the operator sought a different approach which included the deployment of a specialized stimulation treatment, which is a mixture of organic acids, solvents and clay inhibitors with built in corrosion sequestration and de-emulsifiers via CT.

This specialized two-fluid treatment comprising of pre-flush and main treatment was sequentially pumped and allowed to soak for 5hrs and 36hrs respectively.

CT run planned to be performed with a jetting tool run across the SAS was not feasible as there was no access to the bottom of the SAS assembly as several attempts to mill out the HUD encountered in the tubing string proved abortive.

This paper aims at presenting advances in barite dissolving capability with non-damaging stimulation fluid and powerful "descaler" which although reacts quicker in warm environments (>100°F), is not largely temperature dependent to reach depletion with normal reactions taking place within 24hours. The post stimulation results and recovered debris validates the dissolving capabilities for cleaning sulphates of barium, strontium and calcium as well as calcite in wellbores.

You can access this article if you purchase or spend a download.