The Chemistry Prediction and Treatment of Scale Containing Naturally Occurring Radioactive Materials (NORM) in Antrim Gas Fields, Michigan

Abstract

Summary BaSO4 scale containing Naturally Occurring Radioactive Material (NORM) as well as calcium carbonate scale has been reported in gas production facilities in conjunction with the Antrim play in northern Michigan. The scale study was undertaken by the Water Research Institute, Inc. (WRI) under contract from the Gas Research Institute. It was proposed in the scale study to conduct a two phase systematic characterization of BaSO4 scale from the Michigan Basin area both as to occurrence and environmental hazard, and to evaluate scale control methods using brines typical of the area. The initial study involved sample collection and analytical work-up to arrive at a correct theoretical analysis of the problems involved. The variability of the sulfate concentrations in the wells is addressed and scale prediction techniques applied to the reservoirs and the surface equipment to determine where scale was forming and where it is likely to form. The scale is proposed to be forming due to the commingling of produced waters from wells with high sulfate concentrations with waters from other wells relatively high barium concentrations. Inhibitor evaluations were done using a high temperature-pressure laboratory apparatus developed at Rice University and WRI (patent application pending with GRI) and effective chemicals and probable dose rates for inhibition were determined. Concurrently, studies were begun by Bioindustrial Technology, Inc. and United Exploration and Development Consultants to learn the sources of the high sulfate concentrations reported in some wells in the area and to determine the causes of souring in some others. In addition to the scale forming in the surface facilities, NORM scale was predicted and found in production tubing from individual wells. The driving forces for scale precipitation in these wells is the temperature and pressure changes resulting from production Chemical squeeze of inhibitor into the reservoirs and surface injection are recommended to treat and eliminate the scale problem.

A New Approach to Inhibitor Squeeze Design

“…θ u is the dissociation fraction of the polymer C is the bulk concentration of the inhibitor (mg/L) at a given time (t, sec) k mass transfer (cm/sec) is the mass transfer coefficient SSA solid is the solid surface area (assumes 10,000 cm 2 /g) P solid is the solid density (≅ 2.5 g/cm 3 ) θ is the porosity of the formation (≅ 0.1−0.2) C eq is the solubility of the Ca-Phn salt (mg/L) k is the first order rate constant k 1 , k 2 , and k 3 1 Amorphous phase is the initial precipitate, the aged phase is the low solubility phase that was developed after washing the metal phosphonate salt with a large volume of synthetic brine by filtration, and the crystalline phase is the low solubility material that was developed from the amorphous material after washing the metal-phosphonate salt with a large volume of brine by filtration and the crystalinity of the solid has been confirmed with XRD analyses. 2 The solubility is estimated at 70 ºC, 75,490 mg/L TDS, 4,000 mg/L Ca, and pH 5.5. 3 The solubility is estimated at 70 C, 75,490 mg/L TDS, 40 mg/L Fe, and pH 5.5. c. d. b.…”

Low molecular weight poly(acrylic acid) as a salt scaling inhibitor in oilfield operations

“…Worst of all, oilfield scale also contains naturally occurring radioactive materials (NORM). The amount of NORM in the USA has been reported to be 300,000 to 1,000,000 tons per year [1]. Of these salts, barite (barium sulfate) induces incrustation faster because of its low solubility in water, 2.4 mg l -1 , while CaCO 3 , CaSO 4 , SrSO 4 , and NaCl have solubilities of 6.92, 1053, 99.76 and 350,000 mg l -1 , respectively.…”

A New Approach to Inhibitor Squeeze Design

“…There are several parts to understanding and optimizing, in a predictable manner, inhibitor squeeze designs. However, most of the previous efforts have been focused on describing what happens and when to re-squeeze [1][2][3] . There has been virtually no work done on the initial interaction of inhibitors with core materials in a descriptive manner that can be used for engineering design and improvement.…”