Land Treatment of Petroleum Hydrocarbon-Based Drill Cuttings: Pilot Scale Field Study

Abstract

Abstract A pilot scale feasibility study was initiated to evaluate the feasibility of landfarming diesel mud residues in southeastern Oklahoma. Results indicated that land application of diesel residues is an environmentally acceptable disposal method. In a plot with an initial oil and grease (O and G) loading rate of 7.6%, the O and G content decreased by 89.5% during the 209-day study interval. Addition of nutrients enhanced degradation rates and reduced O and G levels below the 1% phytotoxic threshold. An O and G loading rate of 5.8% resulted in no measurable hydrocarbon migration in the soil profile. BTEX levels in leachate samples did not exceed drinking water standards. Total metals measured in the zone of incorporation did not exceed guidelines for limiting constituents. Seed germination studies suggested that landfarming operations could be revegetated within 180 days. Introduction The Oklahoma portion of the Arkoma Basin is a very active natural gas exploration and production region. Typical exploration and production wells are drilled to total dept[is of 14,000–17,000 ft. Diesel-based drilling muds are used because of their desirable rheological properties and value in maintenance of wellbore quality. Approximately 12,000 ft of diesel-contaminated drill cuttings are produced while drilling a single well. Disposal of hydrocarbon-based drill cuttings is a major problem for E and P operators. Disposal options for hydrocarbon-based drill cuttings include burial, landfilling, incineration, solidification, mixing with fly ash and road spreading, and land farming. The preferred disposal method in south-eastern Oklahoma is to mix the cuttings with fly ash and spread on lease roads or production sites. This study was initiated to evaluate the feasibility of land farming diesel mud residues. Soil can be considered a large bioreactor which biodegrades hydrocarbons and converts them into environmentally safe forms. The objectives of this study were:To evaluate the potential of native soil bacteria to degrade the hydrocarbon component of the diesel mud residues.To determine biodegradation rates.To determine if biodegradation rates could be enhanced through addition of nutrients.To determine the effect of landfarming on levels of metals and salts in the soils.To evaluate the potential of landfarming to adversely effect groundwater.To determine when soils treated with diesel mud residues could be revegetated.To determine if hydrocarbons, salts or heavy metalsl each from fly ash/diesel cuttings mixtures. Materials and Methods Construction of Test Plots The Oklahoma Corporation Commission (OCC) approved this pilot study with the stipulation that all runoff and leachate from the test plots must be collected and properly discarded. Figure 1 illustrates a plan and cross-section view of a test plot and associated leachate collection system. P. 149^