Nitrogen/heat generating system (N/HGS) is a thermal-chemical method comprising huge amounts of heat and nitrogen gas generated by reaction between two nitrogen-containing aqueous salts, ammonium chloride and sodium nitrate. The inherent properties of this system make it a good additive in matrix acid stimulation and clean-up treatments for heavy oil wells. The generated heat tends to reduce the oil viscosity, thus enhancing oil mobility while the generated nitrogen gas will reduce hydrostatic pressure of the oil column. Both actions will help the reservoir to better cleanup. Lab results showed that N/HGS was effective in removing oil-based mud filtercake damage. Application of N/HGS cleanup fluid in HP/HT filter press cell was associated with an increase in pressure of more than 100 psi and in temperature of nearly 40°C. An optimized N/HGS formulation was very effective on filtercake removal; nearly 81% of flow efficiency was obtained. The N/HGS formulation contains in addition to the basic nitrogen-containing salts an organic acid, an emulsion breaker and a viscosity reducer. The organic acid, acting as a reaction catalyst in N/HGS, is also proposed to dissolve bridging material presents in filtercake, calcium carbonate. Application of this system, for first time in Saudi Arabia, to remove oil-based filtercake damage from a sandstone horizontal well was very successful. The N/HGS components were pumped in a way to be mixed in the wellbore of the horizontal section. Coiled tubing was used to pump one component while the other component was pumped through the annulus. The reaction of N/HGS components was associated with generation of huge heat as detected by the Distributed Temperature Survey (DTS) which showed that reservoir temperature increased from 153 to more than 300°F. Following the N/HGS treatment, the dead well was able to produce naturally with a competitive production rate compared to offset wells treated with conventional clean-up fluids.

Mono and diamine compounds were synthesized from 1, 12-dodecanediamaine, and evaluated as acid corrosion inhibitors for coiled tubing steel. The inhibition behavior of these compounds in concentrated HCl acid was examined using a gravimetric method. Weight loss tests were conducted in 28 wt% HCl acid at 60, 70 and 80 o C for 2 hours. The results showed that both mono and diamine inhibitors exhibited a good protection efficiency for coiled tubing steel in 28 wt% HCl acid. However, monoamine compounds showed better performance. Addition of an intensifier was effective to enhance protection efficiency for both amine moiety compounds where more than 99% protection was obtained for some inhibitors. The effect of intensifier concentration on inhibition efficiency is also addressed in this paper. The results obtained are very promising and suggest that some of examined corrosion inhibitors have a good potential to be used in acid stimulation treatments of oil/gas wells.

Organic deposit including asphaltene and paraffin may damage the near wellbore area and obstruct production tubings resulting in partial or total loss of well productivity. Most of asphaltene deposits are associated with paraffin. This paper presents a first successful field application of a lab proven/optimized chemical solvent to remove organic deposits from a dead oil well in a sandstone reservoir. A vertical gravel-packed oil producer well was dead due to deposition of organic material in 3 ½" production tubing forming obstruction to flow. The deposition is expected to take place due to long shut-in time as experienced in this well with high GOR. A bailer samples was obtained from this well. Analysis of the obstructing material indicated that they were mainly asphaltene associated with paraffin. Solubility of obtained organic deposits in several solvents was evaluated at reservoir temperature (188°F) and monitored as a function of soaking time. Several criteria were considered in selecting of the optimal solvent formulation, among which were safety and solvency power. The selected formulation incorporates asphaltene dissolver solvent and paraffin dissolver solvent in addition to surfactant. Application of the optimal solvent formulation, that exhibited the maximum solvency power in a minimum soaking time, was very effective in restoring well productivity while minimizing operational cost. A total of 12 feet of obstructing organic deposits were removed from the production tubing using coiled tubing in a multi-stage treatment. Following, the solvent was squeezed into the formation across the screens to maximize cleaning efficiency at the source. The sustainable oil production rate obtained and asphaltene content in flow back samples indicated that the treatment was very successful. To prevent further asphaltene/paraffin precipitation during shut-in time, asphaltene/paraffin inhibitor is recommended. A detail of asphaltene/paraffin formation mechanism, lab evaluation and field application results will be addressed.