• define the following reservoir properties and understand their importance in the overall reservoir development scheme:
  • Rock properties: porosity, permeability, fluid saturation, compressibility, anisotropy
  • Fluid properties: phase behavior, PVT relationships, density, viscosity, compressibility, formation volume factor, gas-oil ratio
  • Rock/fluid interactions: wettability, interfacial tension, capillary pressure, relative permeability
• read and understand wellsite descriptions of recovered core material, evaluate the core handling and preservation techniques employed, and select sample intervals for laboratory analysis
• generate a procedure for preparing and analyzing selected core samples, specifying the tests to be run and the information to be obtained; describe the laboratory techniques and perform the calculations used for determining rock properties
• design procedures for obtaining representative surface and subsurface formation fluid samples
• describe procedures for generating PVT analyses of reservoir fluid samples, and interpret the resulting reports
• use published correlations to estimate reservoir fluid properties

You will be in charge of obtaining representative fluid samples and determining their Pressure-Volume-Temperature (PVT) characteristics. You will also design a coring and core analysis program for a new well, and use the results to define basic rock properties and rock-fluid interactions.

The discovery well, Well 4E1-NE, tested at 1550 STB/D of 35 degree API oil [246 m³/D, 0.85 specific gravity], with a producing gas-oil ratio of 680 SCF/STB [121 m³/m³] and a water cut of about three percent. It is currently on an extended production test.

The second well drilled in this field , Well 5C1-SW, tested all water and was subsequently suspended.

Before your company acquired these drilling blocks, a medium-sized independent had run a series of seismic surveys in the area. Your company purchased these data, from which the Geology and Geophysics departments constructed a subsurface contour map showing the approximate structure boundaries and the top of the Upper Sand.

You are now part of the interdisciplinary team charged with characterizing the reservoir and developing an optimal exploitation strategy. Right now, you do not have much to work with—just the contour map and the well data obtained so far. (You can access this material by clicking on the References that accompany each assignment question.)

What you will need to do at this point, then, is to use the available data to try to define some basic reservoir rock and fluid properties.

• define the following rock mechanical properties under various conditions of confining pressure, describe how these properties influence wellbore stability, directional drilling considerations, well completion design and other aspects of reservoir development, and know how they are measured in the laboratory:
  • Brinell hardness
  • Tensile strength
  • Normal/shear stress relationships and failure mechanisms (Mohr circles)
  • Young’s modulus
  • Poisson’s ratio
  • Compressive strength
  • Shear strength

In this assignment, you will define rock mechanical properties based on an analysis of core samples from Well 2A5-NE. You will:

	(1)	select core samples for measuring rock mechanical properties
	(2)	estimate the overburden and pore pressuress at reservoir depth
	(3)	determine rock mechanical properties under reservoir conditions
	(4)	calculate rock compressive strength, Young's Modulus and Poisson's ratio,
	(5)	Use a Mohr diagram to interpret the reservoir's shear stress rate

• identify the presence and orientation of fracture systems in the reservoir

We then apply this empirical knowledge to the formation by combining our core observations with such geologic information as well logs, structure maps and regional outcrop studies.

In this assignment, you will review core descriptions for evidence of natural fractures and other tectonic activity. You will then incorporate your observations with other data sources to determine the principal stress directions in the formation.

Core analysis, including rock mechanical properties tests, have been done on selected samples from Well 2A5-NE. Early seismic measurements and log data from offset wells indicate that the reservoir is bounded by normal faults on the east and west.

Your objective in reviewing this core information is to

	(1)	determine the formation’s principal stress directions,
	(2)	and find indications of tectonic activity.

• identify primary reservoir drive mechanisms (solution gas drive, water drive, gas cap drive) by observing production and pressure trends.
• estimate original hydrocarbons in place, using both volumetric and material balance methods, and develop a range of estimates for technical recovery factors and reserves.

In other words, we need to determine , respectively, the oil and gas in place, the reserves, and the production rate.

Your job in this assignment scenario is to review the reservoir data that have been collected to this point and

• estimate the original hydrocarbon in place using volumetric and material balance methods,
• qualitatively evaluate the reservoir drive mechanisms, and
• estimate the reservoir’s primary recovery factor

• use the MS Office suite of applications (Word, Excel, Powerpoint, Access, etc.) to produce word-processed documents, generate simple graphics, lay out and manage spreadsheets, develop presentations, manage databases, and perform other day-to-day tasks.
• access and use reservoir engineering applications that are common to PDVSA, whether they be company-specific or "off-the-shelf" programs, to formulate and solve reservoir problems.

	(1)	The four software programs that are bundled in the Microsoft Office suite: Word, Excel, PowerPoint, and Access.
	(2)	Eleven Reservoir Engineering software programs developed by two service companies: seven programs from Schlumberger, and three from Landmark Graphics; and

A comprehensive treatment of these software applications is outside the scope of this assignment. Its objective is rather to build your understanding of these applications and to test your familiarity with their basic features.

• demonstrate a basic knowledge of disciplines outside of reservoir engineering (i.e., Geology, Sedimentology, Petrophysiscs, Geophysics, etc.), and establish a working relationship with specialists from these disciplines.
• understand the role of different disciplines in the overall process of reservoir characterization and exploitation.

In this assignment, you will review the well and field data that have been gathered to date for the Upper/Middle sands, so that you can have an idea of what tools are available for describing the subsurface environment. You will also look at how various E&P disciplines may fit into the overall reservoir management task.

• contribute to the well planning process by understanding the reservoir engineering aspects of the proposed work and having a knowledge of drilling, workover and well servicing fundamentals
• work with the geologist and the drilling engineer to select well locations, target depths and casing points

• select the proper sizes and grades of tubulars to maintain the integrity of the wellbore and handle anticipated production
• select the downhole casing and tubing accessories needed to optimize production and future well work

In this assignment, you will work on the well's completion design. You will select the completion type and tubing configuration, specify the casing and tubing diameters to be used, and design the surface and production casing strings.

The success of your design will depend on how well it handles the anticipated production, compatibility of the various hole, casing and tubing sizes, adequacy of the casing design loads, and cost.

• evaluate the features, benefits and limitations of various mud systems and additives, and select the one most appropriate for a given well
• specify controls on fluid properties in order to optimize drilling and workover operations

The AFE for drilling Well 5A1-SW has been approved, and operations are getting underway. Once drilling begins, your job will be to closely monitor the properties of the mud system you have selected, and to make changes in the mud system as operating conditions may require.

• determine the pressure losses that occur in the rig circulating system
• use basic calculation methods to determine optimal bit nozzle size, annular velocity and other rig hydraulics parameters
• diagnose drilling problems resulting from poor hydraulics practices

The easiest way to control and optimize drilling hydraulics is to select the appropriate bit nozzle diameters for delivering the maximum amount of hydraulic energy to the bottom of the hole.

In assignment, you will learn to use drilling hydraulics principles to maximize penetration rates, ensure hole stability, optimize hole cleaning characteristics and minimize formation damage.

By the time you complete this module, you should be able to determine pressure losses in the rig circulating system and select the appropriate bit nozzle diameters for optimizing hydraulic energy.

• determine the volume, displacement and density requirements for cementing a casing string
• select the cement additives appropriate to a given job
• specify the casing accessories to be use on a primary cement job
• outline the steps involved in cementing a string of casing
• evaluate the results of a primary or squeeze cementing operation
• calculate the volumes and displacements required to set a cement plug

Well 5A1-SW has been drilled to T.D., and the openhole formation evaluation program has been completed. It is now time to run and cement the production string. The purpose of this primary cement job, in which cement slurry is pumped down through the casing and up the casing-hole annulus, is to form a seal between the casing and formation, and to support the weight of the casing string.

In this module, you will determine how much cement you need for the production casing, what materials and additives you should use, what casing accessories and equipment you need, and what procedures you should follow. You will then evaluate the success of the primary cement job and, if necessary, recommend remedial work.

• identify reservoirs that are suitable candidates for horizontal or multilateral wells
• apply knowledge of the reservoir to a selection of the well trajectory
• select the best general completion design for a horizontal or multilateral well in a given reservoir

In this assignment, you will define basic directional drilling parameters and establish the trajectory for a possible re-drill of an existing well. You will look at the feasibility of horizontal and multilateral wells from a reservoir management perspective, and consider some of the issues involved in planning and designing these wells. By the time you complete this module, you should be able to calculate a simple well trajectory, identify candidate reservoirs for horizontal wells and select the best general completion design for a given reservoir.

Well 5C1-SW was the second well drilled in the Upper/Middle sands. Detailed log analysis and an open hole formation test indicated that the top of the Upper Sand at 14800 ft [4511 m] was below the oil-water contact. The well was subsequently plugged back with cement to the surface casing and suspended

Several members of the reservoir management team have suggested re-drilling this well upstructure to Block 5B1-NE. The drilling department will evaluate the feasibility and costs of re-drilling from below the surface casing. Your job will be to establish some of the basic directional parameters and calculating a trajectory for this well, which will be designated 5C1-SW R/D.

• select the optimal completion design and the proper surface and subsurface equipment for producing a flowing oil well efficiently and economically
• optimize flowing well performance based on knowledge of inflow performance, vertical lift performance and surface choke performance
• determine when artificial lift will be necessary in order to maintain oil production at desired levels, and select the most appropriate lift method for a given well
• specify design and equipment requirements for placing a well on artificial lift

Well 5A1-SW has been recently drilled to the Upper/Middle sands. It is to be completed by selectively perforating the 7-inch casing, which has been cemented at a depth of 14400 ft. In this module assignment, you will review actual and estimated field data, select the general well configuration, and specify requirements for subsurface producing equipment. You will define the well's inflow performance relationship (IPR), determine its vertical lift performance for various producing rates, and establish surface flow parameters. You will then combine these analyses to define and predict the flowing well's performance. You will also review various artificial lift methods to determine how this well will be produced once it can no longer flow.

• analyze well behavior, using nodal analysis and interpreting historical production trends
• diagnose equipment problems and/or detect production deviations
• identify production problems relating to pressure decline, water, gas or sand production, low productivity, formation damage or equipment failure
• recommend actions required for optimizing production, identify candidate wells for well servicing, stimulation and/or sand control and indicate the best method to use

Well 5A1-SW has been completed in the Upper/Middle sands, and a production and buildup tests have been completed. You now need to see if the well's actual performance matches what was predicted before its completion. You will be looking for ways to optimize this well's production under both current and future reservoir conditions. You will also look at other wells, including two that are currently producing using electric submersible pumps and one that is planned as a rod pump completion, and make recommendations regarding their performance.

• determine fluid handling and transport requirements for surface facilities and equipment
• identify the surface facility components needed to handle the field's production, specifying their capacities and pressure ratings
• generate a general surface facilities layout showing the path of the produced fluids from the wellhead to the transportation point (pipeline or loading rack)

A production forecast has been generated for the Upper/Middle sands based on extended production tests and currently available rock and fluid data. You will decide how to use this forecast in sizing the surface facilities, and you will determine what types of fluid handling, separation and treating equipment will be needed. You will also specify the path that the produced fluids will follow through the production facility. Although your work will be of a very preliminary and general nature, it will be instrumental in future cost analyses, budget planning, and, ultimately, selection of an optimal reservoir development scenario.

• select candidate wells for testing and specify test objectives
• design a pressure transient test and select equipment in keeping with the stated objectives
• monitor the test and interpret the results

Formation evaluation of the Upper/Middle sands--including successful production tests of Wells 4E1-NE and 5A1-SW--has established this reservoir's commercial hydrocarbon potential. The reservoir management team has generated estimates of oil in place and recovery factors; it has even predicted a production schedule and outlined basic surface facility specifications. These estimates are, however, very preliminary, and based on assumptions which may or may not prove valid over time. There is still a good deal of appraisal and planning to be done before the reservoir moves into the development stage of its life.

Your assignment in this Learning Module is to assist in the reservoir appraisal by developing general guidelines for a well testing program, based on your understanding of formation evaluation objectives and test procedures. You will also be looking at DST results from wells in other fields so that you may become familiar with basic methods of test monitoring and interpretation. In later assignments, you will become more involved in the analysis of pressure transient tests, particularly with respect to modern interpretation methods.

• access PDVSA engineering and geoscience databases and identify information that is relevant to the field under study.
• classify information according to discipline and what reservoir parameters it helps to define.

In this Learning Module assignment, the reservoir is in the early appraisal stage of its life. Its status at the time of this assignment is as follows:

• A structure contour map has been generated from seismic data and interpretations of regional geological data.
• Well 4E1-NE, the discovery well, is currently on an extended production test.
• Well 5C1-SW tested all water, and was subsequently suspended.
• Drilling is in progress on Well 2A5-NE. A conventional coring program has been authorized, and should be getting underway soon.

The reservoir management team is already at work compiling a database of reservoir information. Your job in this assignment is to provide some ideas of what this database can contribute to the task of reservoir management, and what information should be added to it.

• select the appropriate logging tool(s) for evaluating a given reservoir prameter, taking into account operating conditions and limitations.
• specify procedures, surface equipment, and auxiliary tools to be employed on a logging job.

Conductor casing has been set at Well 2A5-NE, and the surface hole is currently being drilled. Your tasks in this assignment are to review the surface logging program, and then to select the appropriate tools for logging from Target Depth to the shoe of the surface casing.

• monitor the quality control of logging procedures, including calibration, correction and choice of scales)

You are approaching target depth on Well 2A5-NE, and you will shortly be calling out the service company crew to log the 8 1/2 inch hole interval. Your job in this assignment is to establish some general guidelines for conducting logging operations, review tool calibrations and monitor survey progress.

• Use log analysis to identify reservoir rock properties (fluid saturation, porosity, fluid contacts, permeabilities, bulk shale content, net oil sand, fractures)

The open hole formation evaluation program at Well 2A5-NE is in progress, and field copies of the lithology, resistivity and porosity logs are now available. Your job in this assignment is to review these logs and make an initial evaluation of the well's hydrocarbon potential. Your evaluation is an important first step in deciding whether to complete the well, so be sure to carefully examine the log data.

• generate geologic cross sections from well logs.
• draw subsurface contours and construct geologic and geophysical maps.

To complete the assignment, you will consider several additional formation parameters that may be conducive to subsurface contour mapping, and consider how they could be used to describe this reservoir.

• access the applications used to generate MEM maps in official formatt
• generate a map using the applciations.

The Ministry's organization and objectives are basically the same as those of the Ministry of Energy and Mines (MEM) in the neighboring Republic of Venezuela, and the norms that it has established for oil and gas operations are identical to MEM standards. For this reason, the questions that you are asked in this assignment use MEM standards as primary reference sources.

To access the MEM references, click on the "Practical Knowledge" link

In this Assignment, you will review the present status of the Upper/Middle sand reservoir, determine what reports you need to submit to the Ministry, and decide how to classify well locations and estimated hydrocarbon reserves in keeping with established norms. You will also ensure that the symbols and conventions used in the official maps that are submitted with these reports are consistent with Ministry standards. By the time you complete the Assignment, you should be able to comply with MEM standards for reporting reserves and generating subsurface maps using accepted symbols, conventions and nomenclature.

The current status of the Upper/Middle sand reservoir is as follows:

• Well 4E1-NE, the discovery well, is on an extended production test. Permanent completion is pending.
• Well 5C1-SW was suspended after well logs and a formation test indicated that it exposed the Upper Sand below the water-oil contact.
• Well 2A5-NE has been drilled and tested, and a successful open hole formation test has been carried out.

• measure compaction, subsidence parameters.
• determine the significanc of these parrmeters with re determining drive mechanisms, etc.

Compaction also takes place when fluids are withdrawn from a subsurface formation. Fluid withdrawal causes a decrease in pore pressure, which in turn increases the grain-to-grain, or matrix pressure of the rock particles and causes them to compact. The amount of compaction that occurs in a given formation depends only upon the difference between the vertically applied overburden pressure and the fluid, or pore pressure. Thus, the uniaxial compaction of a rock sample of thickness h can be expressed as

     DV_b/ V_b = Dh/h

Depending on geological conditions, subsurface compaction may be associated with varying degrees of subsidence, or sinking of the ground at the surface.

Compaction and its associated effect of surface subsidence can, in certain situations, have significant effects on reservoir management strategies and field operations. In this Assignment, you will build your general understanding of these phenomena and see how they can influence reservoir engineering decisions. You will also look at a system that has been developed by PDVSA to describe and predict compaction and subsidence in areas where they are of particular concern.

By the time you complete this assignment, you should be able to identify situations where compaction and subsidence may be important considerations in a reservoir management strategy, and you should be able to begin using computer-based tools for predicting compaction and subsidence under various conditions.

PLEASE NOTE:The Assignment for this Learning Module refers to the HUNDCALC subsidence prediction system developed by PDVSA (Maraven), and described in the document Procesos Operativos y de Calculos Del Sistema de Prediccion de Hundimiento "HUNDCALC" (REN-836, author Carlos Wulff, November 1994). If you cannot access this document through your company's Intranet, or by clicking on the "Practical Knowledge" link, please contact your mentor or system administrator.

• review and acquire well test information
• validate pressure test information
• prepare well test data for analysis
• diagnose and interpret the pressure test
• design and interpret production records; analyze production behavior

• Establish the areal and vertical distribution of zones with similar behavior in agreement with the reservoir model.
• Identify and delineate the rock volumes with sedimentological, petrophysical and reservoir properties that enable hydraulic communication.

The purpose of geological mapping is to identify flow units that contain oil and gas, and once they are found, to apply geologic evidence and concepts toward achieving the most efficient development and production of these prospects. However, it is important to remember that these geologic maps are never finished. When new wells are drilled or old