This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 178996, “Removing Formation Damage From Fines Migration in the Putumayo Basin in Colombia: Challenges, Results, Lessons Learned, and New Opportunities After More Than 100 Sandstone-Acidizing Treatments,” by Wildiman Reinoso, Fredy Torres, and Manuel Aldana, Grantierra, and Pablo Campo, Emilce Alvarez, and Erika Tovar, Halliburton, prepared for the 2015 SPE International Conference and Exhibition on Formation Damage Control, Lafayette, Louisiana, USA, 24–26 February. The paper has not been peer reviewed.
To date, more than 100 sandstone-acidizing treatments have been performed in several Colombian oil fields, targeting the Villeta and Caballos Formations in the Putumayo Basin. Fines migration has been the main damage mechanism treated with this type of chemical stimulation. This paper summarizes a wide variety of sandstone-acid-stimulation case histories, highlighting aspects such as mechanical conditions and operational practices.
Introduction
The Putumayo Basin is located in south-ern Colombia. The Putumayo Basin shows a stratigraphic sequence containing Early Cretaceous (marine) to Miocene/Pliocene sediments (fluvial). Fig. 1 illustrates the location of the Putumayo Basin.
Sand Villeta Formation
The T Sand samples examined are fine-to medium-grained sandstones. They are composed primarily of quartz grains cemented primarily with quartz overgrowths and authigenic clays. Rare-to-minor cements include solid hydro-carbon, pyrite, and dolomite. X-ray-diffraction (XRD) analyses show that all of the sandstone samples are composed primarily of quartz and clay minerals.
Feldspars are absent from all but one sample. Given that virtually all of the framework grains are quartz, with possibly minor argillaceous grains, the sand-stone is classified as quartzarenites. Scanning-electron-microscope (SEM) photographs show authigenic kaolinite filling intergranular zones and possibly replacing grains.
Caballos Formation
Samples in this formation are all sand-stones. Estimated average grain size ranges from very fine sand to medium sand. The framework grain suite is dominated by quartz. The grains are cement-ed primarily by quartz overgrowths and authigenic clays. XRD determined that all of the samples are composed primarily of quartz and clay minerals. Feld-spars are rare to absent from these sand-stones, confirming that virtually all of the framework grains are quartz and the sandstones should be classified as quartzarenites. Clay-mineral content averages 7.8%, with illite and mixed-layer illite/smectite more common than kaolinite. SEM photos show that these clays are authigenic.
