A Novel Non-damaging Approach to Isolate Open hole Lateral that Allowed Performing Mechanical Descaling in the Non-Monobore Cased Completion: A Case Study in Saudi Arabian Carbonate Reservoir

Abstract

Mechanical descaling of iron sulfide scales in high angle non-monobore or horizontal open hole completion offer multifaceted challenges, especially when the reservoir is depleted. The history of the descaling program in carbonate gas wells in Saudi Arabia dates back to 2007. The program suffered several setbacks with operational complexities like stuck pipe, H2S generation (souring) during chemical dissolution and severe induced damage during reservoir isolation process. The depleted reservoir needs to be isolated to ensure full circulation during mechanical descaling process. The mechanical means of isolation with a bridge plug is not feasible due to the presence of FeS scale in the wellbore. The only isolation option available at the moment is CaCO3 chips bullheaded from the surface. Often the post-descaling and stimulation operation does not restore the original production, due to the heavy damage induced in the reservoir during isolation. This paper shares a successful descaling experience and best practices in a single lateral open hole well that was completed with 4-1/2-in tubing and 7-in liner, and had severe pressure depletion. A novel non-damaging visco-elastic surfactant based fluid was used to fill the open hole lateral and as base to support CaCO3 chips above it that prevented additional damage and allowed reservoir isolation for mechanical descaling, using high pressure coiled tubing and a jetting tool. A clean wellbore with no further induced damage made subsequent post-stimulation results very attractive. The paper also presents the production results of stimulation treatment performed after the descaling treatment.

Corrosion and Scale Formation in High Temperature Sour Gas Wells: Chemistry and Field Practice

“…It has been found that a fluidic oscillation technology cleaning device (Webb et al 2006, Leal et al 2007, Buali et al 2014) and a high pressure jetting tool with a down-hole motor or turbine with mills (Bolarinwa et al 2012, Mukhliss et al 2014) are effective in removing iron sulfide scales. Current mechanical procedures involve temporary reservoir isolation without formation damage (Buali et al 2014, Mukhliss et al 2014.…”

“…Current mechanical procedures involve temporary reservoir isolation without formation damage (Buali et al 2014, Mukhliss et al 2014. In a severely scaled well, the differential of pressure between the pressure upstream of the choke and downstream of the choke is not changed even though one has decreased the choke of the well.…”

“…In one instance 316 kg of solid materials were recovered at the surface. Well descaling efforts have allowed increased well gas production and overall obtainable gas reserves (Buali et al 2014, Mukhliss et al 2014.…”

“…Strong mineral acids can cause rapid generation of hydrogen sulfide (Wang et al 2013). Both iron control agents and hydrogen sulfide scavengers interfere with the dissolving power of hydrochloric acid (Nasr El-Din et al 2000). Okocha (2011) studied the effect of tetrakis (hydroxymethyl) phosphonium sulphate (THPS) as a sulphide scale dissolver.…”

“…Iron sulfide scale formation in water supply wells and sour oil and gas wells was investigated in earlier work (Nasr El-Din et al 2001). Iron sulfide scale was obtained in an oil well with low water cut (Nasr El Din et al 2001).…”