IDENTIFICATION OF WELL PROBLEMS USING WELL TESTING (A CASE STUDY OF UMU-N2 WELL OF MIDWESTERN OIL AND GAS COMPANY, KWALE, NIGERIA)

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ABSTRACT

Well tests exist already for a long time. Since the first oil reservoir was discovered, oil companies have always been keen on estimating reservoir properties such as size. Present day well testing has gone beyond this and its usefulness cannot be overemphasized. This project work is concerned with the use of well testing in identifying well problems. The case under study is the UMU-N2 well of Umusadege field, Kwale. From analysis of the well test data, it was seen that the well had impairment which was due to reduced permeability and thus, required stimulation for improved recovery of the hydrocarbons present. Also, there was high sand and water production which also reduced the productivity of the well.

CHAPTER ONE

1.0 INTRODUCTION

In the petroleum industry, awell test is the execution of a set of planneddata acquisitionactivities to broaden the knowledge and understanding of hydrocarbons properties and characteristics of the undergroundreservoirwherehydrocarbonsare trapped. The overall objective is identifying the reservoir’s capacity to produce hydrocarbons, such asoil, natural gasand condensate. Data gathered during the test period includesvolumetric flow rateand pressure observed in the selected well. Well testing can be surface or subsurface testing and each type has its own objectives. A properly designed, executed and analyzed well test usually can provide information about formation permeability, extent of wellbore damage or stimulation, reservoir pressure, reservoir boundaries and heterogeneities etc. Outcomes of a well test, for instance flow rate data andgas oil ratio data, may support thewell allocationprocess for an ongoing production phase, while other data about the reservoir capabilities will support reservoir management. A well is said to have problem when its behavior deviates from the normal production pattern. Typical well problems for producing wells include low productivity, low reservoir pressure, formation damage and skin value, high viscosity oil, wellbore and tubing plugging, high gas- oil ratio etc. Hence, well testing is therefore one of the economic source of valuable information about reservoir properties such as porosity, permeability, fluid viscosity, reservoir limit, drainage volume and vertical permeability orientation etc.

  1. TYPES OF WELL TESTING

Generally, Well testing can be divided into three types viz:

  • Pressure transient test
    • Periodic productive testDeliverability testPRESSURE TRANSIENT TEST:This is a means of assessingreservoirperformance by measuring flow rates and pressures under a range of flowing conditions and then applying the data to a mathematicalmodel. During the flow period, thepressure at the formation is monitored over time. Classification of pressure transient test includes pressure drawdown test, pressure build-up test, injectivity test, inference test, fall off test etc. These tests requires higher degree of sophistication and used to determine formation damage or stimulation related to reservoir parameters such as permeability, porosity, pressure, volume etc.PERIODIC PRODUCTIVE WELL TEST: This is a routine test carried out to physically measure oil, gas and water produced by a particular well under normal producing conditions. It helps to determine the daily production of oil, water and gas. These information serve as an aid in well and reservoir operations and also in meeting legal and regulatory requirements.DELIVERABILITY PRODUCTIVITY TESTS: This is an intensive oil and gas well test which involves the physical or empirical determination of fluid flow rate versus bottom hole pressure drawdown with a limited number of measurements in order to determine the capability of the well under various degree of pressure drawdown. This test is usually carried out on a newly completed well. Results may be used to set allowable production and in the selection of artificial lift system and production facilities. Classification of deliverability tests include Inflow performance relationship (IPR) test, flow after flow test, isochronal test, Potential test etc.
    • AIMS/OBJECTIVES:
      • To study the various types of well tests carried out in the oil industry and how they can be used in identifying well problems.
      • To analyze well test data gotten from UMU-N2 well in order to determines its reservoir characteristics by the application of well test knowledge.
      • To make conclusions on the state of the UMU-N2 well on the basis of data analysis and give possible recommendations.