In recent years, there has been tremendous growth in multistage fracturing for unconventional plays employing multistage fracturing completion systems with openhole (OH) packers or cementing to isolate multiple stages and ball-activated frac sleeves with graduated seats (traditional graduated-seat frac sleeves) to divert the fracturing treatments. This phenomenon has developed primarily because these systems not only maximize production, but also save significant completion time and money with the ability to perform multiple stimulations in a single trip, with minimal or no thru-tubing intervention. However, traditional ball-activated frac sleeves have graduated ball seat sizes for each additional zone, and therefore, each ball seat creates its own backpressure within the system. With the number of frac stages increasing, the ball seat sizes become smaller, leading to an increase in the surface pressure and hydraulic horsepower (HHP) required to generate a given net downhole pressure or flow rate. In order to solve these limitations, a revolutionary ball-activated fracturing system has been developed, which can be installed with an unlimited number of zones using a single size ball and ball seat for each zone. This new technology can greatly reduce frictional forces and enables a more efficient fracturing of each zone within the wellbore. Most importantly, this new frac sleeve is sized to achieve an inside diameter (ID) as close as possible to the host tubular string, thus requiring a much lower fracturing pressure on the surface compared with traditional graduated-seat frac sleeve. This paper will present the operational mechanisms of this new frac sleeve, simulation of frac efficiency and financial analysis with quantitative comparisons between it and traditional graduated-seat frac sleeve. The analysis will indicate that this new frac sleeve technology can be used to optimize hydraulic fracturing operations in both HHP requirements and stimulated reservoir volume (SRV) while dramatically reducing operational time and overall completion costs.

Summary Deep, hard, or directional drilling imposes extraordinary stresses on drillstring components. Because of theadditional economic risks of deep drilling, the inspection and acceptance of drillstring components should be based ontheir compliance with API and user standards. Inspection procedures that provide the highest probability of finding procedures that provide the highest probability of finding and eliminating unacceptable components should be used. Often, too much reliance is placed on a "report" or"certification" that the drill string components have been"inspected, "The operator assumes that because the material has been inspected, it is suitable for the intended service. This paper addresses three areas in which the above approach may lead to trouble.Widespread, established practices have resulted insome applicable API guidelines being unintentionally ignored by users and inspection companies.API standards for used drillpipe do not address someitems of concern to operators engaged in deep or critical drilling.Inspection companies frequently do not followsimple quality control steps that can markedly improve theresults of their work. Examples of shortcomings in current industry practicesare given. Corrective actions implemented by several companies in the last 12 to 18 months are also given. A hand-held calculator program that will aid in evaluating the wear limits on rotary shouldered connections isprovided in the Appendix. provided in the Appendix. Drillstring Failures Examples of drillstring failures are well documented inliterature. 1 Unfortunately, they are also all too familiarto most drilling engineers and operations managers fromfirsth and experience. Common in-service failures include the following.Fatigue cracks can be induced by cyclic loading inhigh-stress areas of connections and drillpipe tubes(Fig. 1).Washouts caused by leaking drilling mud can erodemetal and enlarge the leak (Fig. 2). Leaks may occur fora variety of reasons, but the most common causes are fatigue cracks, inadequate makeup torque, shoulder sealdamage, or excessive or improper refacing of the shoulders.Tensile breaks occur when the load-carrying capacityof a member is exceeded. This occurs most frequentlyin the tube body (Fig. 3) or in the pin of a connection.Torsional failures occur when the torque applied indrilling exceeds the capacity of a drillstring componentto resist torque. Fig. 4 is an example of a torsional failurein a drillpipe box. Drillpipe failures occur for a variety of reasons. Broadly speaking, these can be grouped into three categories. If a failure occurs eitherthe drill string was designedincorrectly-e.g., the weight and grade were inadequatefor the application;the drillstring was misused-e.g., connections were over torqued during rig floor makeup;ordefective components were accepted and runbecause of inadequate inspection, poor-quality inspection, or poor definition of the standards of acceptance. It has been our experience that persons responsible for drilling wells are much more familiar with the design and proper use of drill strings than they are with inspection proper use of drill strings than they are with inspection processes and acceptance standards for those strings. In processes and acceptance standards for those strings. In the hope of helping to correct this situation, the remainder of this paper addresses some problems and solutions inthe area of drillstring inspection. Drillstring Inspection There seems to be a pervasive attitude among drillingpeople that inspection is someone else's problem. Few oil people that inspection is someone else's problem. Few oil companies would write the following clause into theirday-rate drilling contract. The drilling contractor shall decide well location, well depth, directional program, mud program, logging program, casing and cementing program, and whether the well will be completed or abandoned. Contractor shall provide a report certifying that allthe above was done correctly. On the other hand, most companies do not hesitate todelegate the inspection and acceptance of their drillstring components to their contractor or inspection company. It is still common practice to accept an inspection "report"as proof that the components have been inspected. Frequently, when failures occur, the corrective measure maybe to change inspection companies and to repeat the cycle, without any technical involvement in the inspection process. Our message is that the operator can often process. Our message is that the operator can often substantially reduce his economic exposure to drillstring failuresby becoming involved in the inspection process. JPT P. 1511

The main objectives of this project are:(1) to quantify the microscopic distribution of altered wetting that occurs in oil reservoirs as crude oil components adsorb on rock surfaces, and (2) to apply quantitative descriptions of wetting at the microscopic level to interpretation of imbibition in mixed-wet porous media. AbstractThe questions of reservoir wettability have been approached in this project from three directions. First, we have studied the properties of crude oils that contribute to wetting alteration in a reservoir. A database of more than 150 different crude oil samples has been established to facilitate examination of the relationships between crude oil chemical and physical properties and their influence on reservoir wetting. In the course of this work an improved SARA analysis technique was developed and major advances were made in understanding asphaltene stability including development of a thermodynamic Asphaltene Solubility Model (ASM) and empirical methods for predicting the onset of instability. The CO-Wet database is a resource that will be used to guide wettability research in the future.The second approach is to study crude oil/brine/rock interactions on smooth surfaces. Contact angle measurements were made under controlled conditions on mica surfaces that had been exposed to many of the oils in the CO-Wet database. With this wealth of data, statistical tests can now be used to examine the relationships between crude oil properties and the tendencies of those oils to alter wetting. Traditionally, contact angles have been used as the primary wetting assessment tool on smooth surfaces. A new technique has been developed using an atomic forces microscope that adds a new dimension to our ability to characterize oil-treated surfaces.Ultimately we aim to understand wetting in porous media, the focus of the third approach taken in this project. Using oils from the CO-Wet database, experimental advances have been made in scaling the rate of imbibition, a sensitive measure of core wetting. Application of the scaling group to mixed-wet systems has been demonstrated for a range of core conditions. Investigations of imbibition in gas/liquid systems provided the motivation for theoretical advances as well.As a result of this project we have many new tools for studying wetting at microscopic and macroscopic scales and a library of well-characterized fluids for use in studies of crude oil/brine/rock interactions.iv Table of , where v p is precipitant molar volume. Fits to these linear trends are summarized in Table I relationship used is that for A-93+ α-MN (Fig. I-3.5) with a temperature adjustment of -0.0008 RI units/°C. Solution gas is estimated to be xiii composed of methane, ethane, and propane with mole fractions of 0.5, 0.4, and 0. Figure I-3.27. Measured and predicted onset conditions for flocculation from crude oils induced by precipitants from n-pentane to n-pentadecane. Asphaltene molar volume = 2500 ml/mol. Other model parameters are given in Figure II-2.8. Example of the "memo...

Over the last decade or so, unconventional shale resources have been playing an increasingly important role in hydrocarbon production due to advanced drilling, fracturing and completion technologies enabling the recovery of previously uneconomic reserves, and multi-stage fracturing technology has been widely used to exploit them in the North American oil & gas industry. During that time the completion process has been evolving, starting with the Plug and Perf method and then with multiple ball seat size actuated sliding sleeves gaining attention. However both methods have their drawbacks, the former requiring multiple re-entries and mill out operations, the latter having a limited number of fracturing stages due to the graduated seat sizes needed and the probability of the need for milling out the seats upon completion to remove flow restrictions (Wozniak 2010). As a result of these drawbacks, the industry has been driven to the development of some high-performance multi-stage fracturing completion systems which are emerging in the marketplace as alternatives to both plug and perf and traditional ball-activated frac sleeves. Three such unlimited multi-stage fracturing systems, which have been developed in recent years, can be cemented in place if desired and have a full-bore internal diameter (ID) or as close as possible to the host tubular string after fracturing and do not need milling-out operations, reducing overall completion time and improving fracturing and production efficiency. These include: 1)Coiled Tubing (CT)-Operated sleeve – this incorporates a Bottom-Hole Assembly (BHA) which is used to isolate the target zone and shift the sleeve open with fracturing being performed down the CT/Casing annulus on an nearly unlimited number of sleeves.2)An evolutionary ball-activated frac system – this uses a single size ball and ball seat for each zone, which allows an essentially unlimited number of frac stages.3)Radio-Frequency-Identification (RFID) frac sleeves – by simply dropping RFID tags in the completion string, the RFID frac sleeve system can be run with an unlimited number of frac stages. This paper will review developments in multi-stage fracturing completions, describe in detail their unique features and capabilities which are not available in earlier systems and present simulations of frac efficiency with quantitative comparisons. The analysis will indicate that these three new frac sleeves technologies can be used to optimize hydraulic fracturing operations in both horsepower and stimulated reservoir volume while dramatically reducing overall completion costs.

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Over the last decade productive capacity of both oil and gas from previously uneconomic North American unconventional shale resources has been dramatically enhanced due to advanced horizontal drilling technology combined with multi-stage hydraulic fracturing treatment maximizing access to productive zones. Currently two types of multi-stage fracturing completion systems are in common use: The conventional Plug-and-Perf (P-n-P) method in cased holeFrac sleeves using open hole (OH) packers or cementing to isolate multiple stages To streamline the fracturing process, a new pressure-activated toe sleeve has been developed for both methods which is run in the hole on the bottom of the completion string and actuated after two pressure applications. This sleeve isn't immediately open after the first pressure application, so casing integrity pressure testing can be conducted and pressure can also be held indefinitely to satisfy a range of regulatory requirements. As the second application of pressure is bled down, the sleeve locks open and then composite plugs for P-n-P or balls for frac sleeves can be pumped down to begin subsequent stimulation operations. This toe sleeve is especially beneficial in P-n-P completions, as an alternative to tubing conveyed perforating (TCP) to initiate pump-down operations, eliminating the initial perforation run. As a result the following features and benefits can be realized: This toe sleeve is is hydraulically actuated after two separate pressure cycles applicationsEach pressure cycle application can be held indefinitely for casing integrity pressure testing to satisfy all expected regulatory requirementsThere is no restriction on the time between two pressure applicationsIt eliminates the need for TCP perforating in the first stage of a cemented P-n-P completion at the toe of wellMultiple sleeves can be installed and activated open simultaneously at the toe of the completion stringThe toe sleeve design incorporates port areas sufficient to pump the first stimulation operation, adding an additional zone to any fracturing completion The toe sleeve is fully cement compatibleThis paper will present the operational mechanisms and a case study of the use of this unique toe sleeve which adds significant operating efficiency and lowers the cost of multi-stage fracturing with valid casing integrity pressure test.