Experimental Analysis of Shale for Evaluating Shale Drilling Fluid Interaction in Agbada Formation

Aims: To characterize the shale samples from Agbada formation and to develop an inhibitive water-based mud for the shale types. Study Design: Experimental. Place and Duration of Study: Department of Petroleum, University of Port Harcourt Rivers State, Agbada Formation Niger-Delta Region, between March 2011 and August 2012. Methodology: This study includes the determination of shale properties such as mineralogy, cation exchange capacity, native moisture content and total organic carbon content of the shale samples collected from two wells in Agbada Field. It also involves the establishment of an adsorption isotherm for the shale and the modeling of these isotherms using the Guggenheim, Anderson and Deboer model. Results: Based on the results of the dispersion and swelling tests, 3% Bentonite + 1% Potassium Chloride (KCl) were selected as the promising fluid. Well A exhibited the Type II isotherm which is common to most shale while Well B showed the Type V isotherm. Adsorption isotherm model predictions were in agreement with experimental observations. The samples from the wells exhibited dispersion after testing with deionized water. For Well A and B, 3% Bentonite + 1% Potassium Chloride (KCl) inhibits and yielded higher shale percent recovery values from dispersion tests. Conclusion: It was observed from adsorption isotherm models that the total organic carbon content is not a significant factor in the adsorptive and dispersive behaviors exhibited by the shale samples

Effect of Reversible Invert Emulsion Fluid Additives on The Environment – An Environmental Concern During Drilling Operation

The effect of reversible invert emulsion drilling fluid additives on the soil has been examined in order to evaluate their toxicity and possible environmental impacts that may result from their indiscriminate disposal. Development of effective policies for discharges depends on consideration of the specific local environmental conditions that govern the fate of discharge materials, the scientific basis for assessing the potential for effects in that environment, and balanced consideration of the environmental effects and relative costs of discharge versus other disposal options. This paper reviews the framework that will help achieve general regulatory acceptance of the discharge of reversible invert emulsion mud. In this study, the contaminated soil samples were collected and analysed for metals (iron, copper, zinc, lead, nickel, chromium, manganese, calcium and magnesium) using Atomic Absorption Spectrophotometry (AAS) method. The results showed that Calcium (Ca) has the highest concentration followed by Iron (Fe), Copper (Cu) with varying level of toxic metals like lead (Pb), Nickel (Ni), Manganese (Mn) and Chromium (Cr) in the soil sample. Metals like Fe, Mn and Cu generally have values higher than that of the United States Environmental Protection Agency and World Health Organization Standards thereby implying possible negative impacts on the immediate environments. It is therefore recommended that wastes resulting from oil cuttings and drilling muds should be properly treated before it is disposed into the environment by oil exploration companies

COMPARATIVE APPROACH TO OPTIMUM SELECTION OF ARTIFICIAL LIFT SYSTEM

Artificial lifts are used around the world in approximately 85% of the wells and its overall efficiency cannot be overestimated. The specific lift method for a particular application is largely accomplished by production engineers; they apply both field / operational experience, and modern knowledge. This quality has been recognized as a defect in most engineering disciplines and have led to sub-optimal design in projects. Improper selection of artificial lifts can lead to a reduction in production and a significant increase in operating costs. Once a decision is made about the type of lift that will be installed in a well, whether or not this method is chosen optimally for the existing conditions of the well; very little can be done after installation. This paper analyzed the selection criteria for various artificial lift techniques and illustrate why the selection made is the most suitable technique to be applied in that particular well condition. For optimum decision making, the study considered the characteristics of the reservoir, their operational and design characteristics, the location of the facility and the artificial lift system economic. The economic evaluation of each case was carried out taking into account the capital and operating cost for each option

Data on cost analysis of drilling mud displacement during drilling operation

The focus of this research was to present a data article for analyzing the cost of displacing a drilling fluid during the drilling operation. The cost of conventional Spud, KCl and Pseudo Oil base (POBM) muds used in drilling oil and gas wells are compared with that of a Reversible Invert Emulsion Mud.The cost analysis islimited tothree sections for optimum and effective Comparison. To optimize drilling operations, it is important that we specify the yardstick by which drilling performance is measured. The most relevant yardstick is the cost per foot drilled.The datahave shown thatthe prices fordrilling mud systems are a function of the mud system formulation cost for that particular mud weight and maintenance per day. These costs for different mud systems and depend on the base fluid. The Reversible invert emulsion drilling fluid, eliminates the cost acquired in displacing Pseudo Oil Based mud (POBM) from the well, possible formation damage (permeability impairment) resulting from the use of viscous pill in displacing the POBM from the wellbore, and also eliminates the risk of taking a kick during mud change-over. With this reversible mud system, the costs of special fluids that are rarely applied for the well-completion purpose (cleaning of thick mud filter cake) may be reduced to the barest minimum

Determination of Moisture Adsorption Isotherm of Shale from Agbada Formation Using GAB Model

Shales are susceptible of different phenomena, including swelling, shrinkage and hydration (shale instability); hence are impacted by moisture content. Moisture adsorption isotherms of shales from Agbada Formation were determined at 27oC over a water activity (aw) range of 0.30 to 0.96 using a Static gravimetric technique. Moisture adsorption isotherms of these two shale samples from well A and well B exhibited the sigmoid type II and V shapes respectively. The Guggenhein, Anderson, de-Boer (GAB) model was applied to fit the experimental data satisfactorily. A non-linear regression analysis method was determined to evaluate the parameters of GAB sorption equations. The criteria used to evaluate the goodness of fit to the model were Quadratic estimates, Central derivatives and Conjugate search of Microsoft Excel. The GAB model was used because it fit to the experimental adsorption data for a wide range of water activity (0.10 – 0.96) and the error square value calculated from Microsoft Excel was low. The estimated GAB parameters and constants were in good agreement with what the model dictates and with literature

Data for analyzing drilling fluid ability to effectively achieve hole cleaning for high shear and low shear rates

Rheological models such as Bingham Plastic or Power law models depict fluid behavior with points of the rheological relation which correspond to higher shear rates, but these models are fairly easy to solve for their specific descriptive parameters. Lower rpm (and hence shear rate), could be used to improve the performance and understanding of drilling mud at the lower shear rates prevailing in the wellbore. These data can be utilized in validating these rheological models and the essence of Equivalent Circulating Density (ECD) calculation in analyzing pressure drop in annular hole cleaning

De-emulsification of Nigerian light crude oil using heavy Akylbenzene Sulfonate and its rheological verification

This technical paper evaluates de-emulsification and rheological verification of Nigerian light crude oil emulsion viscosity using statistic model. The light crude oil which is paraffin base, of low wax content was emulsified with brine solution to obtain stable emulsion before deemulsification with heavy alkylbenzene sulfonate. The measurements of the viscosity of the emulsion before and after water separation were carried out using rotational viscometer. Model prediction coefficients of emulsion viscosity, using shear stress and concentrations relationship was established by application of statistical analysis of statistic software version (6). The graphs of observed data versus predicted, shear stress and shear rate data, measured values and predicted values were plotted respectively and 99.954% was obtained as correlation co-efficient. Also, from statistical analysis modeling, the flow behavior index of light crude oil emulsion viscosity is 0.99701, which is approximately 1, which shows the Newtonian fluid behavior

Modelling of Sub-Sea Gas Transmission Pipeline to Predict Insulation Failure

Background: Thermally insulated subsea production and transmission systems are becoming more common in deep-water/ offshore operations. Premature failures of the insulation materials for these gas transmission pipelines have had significant operational impacts. The ability to timely detect these failures within these systems has been a very difficult task for the oil and gas industries. Thus, periodic survey of the subsea transmission systems is the present practice. In addition, a new technology called optic-fibre Distributed Temperature Sensing system (DTS) is now being used to monitor subsea transmission pipeline temperatures; but this technology is rather very expensive. Objective: However, this study proposed a model which will not only predict premature insulation failure in these transmission pipelines; but will also predict the section of the transmission line where the failure had occurred. Methods: From this study, we deduced that in gas pipeline flow, exit temperature for the system increases exponentially with the distance of insulation failure and approaches the normal operation if the failure occurs towards the exit of the gas pipe. This model can also be used to check the readings of an optic-fibre distributed temperature sensors. Result and Conclusion: After developing this model using classical visual basic and excel package, the model was validated by cross plotting the normal temperature profiles of the model and field data; and R-factor of 0.967 was obtained. Analysis of the results obtained from the model showed that insulation failure in subsea gas transmission pipeline can be predicted on a real-time basis by mere reading of the arrival temperature of a gas transmission line