Many tight/shale gas wells exhibit linear flow, which can last for several years. Linear flow can be analyzed using a square-root-oftime plot, a plot of rate-normalized pressure vs. the square root of time. Linear flow appears as a straight line on this plot, and the slope of this line can be used to calculate the product of fracture half-length and the square root of permeability. In this paper, linear flow from a fractured well in a tight/shale gas reservoir under a constant-flowing-pressure constraint is studied. It is shown that the slope of the square-root-of-time plot results in an overestimation of fracture half-length, if permeability is known. The degree of this overestimation is influenced by initial pressure, flowing pressure, and formation compressibility. An analytical method is presented to correct the slope of the squareroot-of-time plot to improve the overestimation of fracture halflength. The method is validated using a number of numerically simulated cases. As expected, the square-root-of-time plots for these simulated cases appear as a straight line during linear flow for constant flowing pressure. It is found that the newly developed analytical method results in a more reliable estimate of fracture half-length, if permeability is known. Our approach, which is fully analytical, results in an improvement in linear-flow analysis over previously presented methods. Finally, the application of this method to multifractured horizontal wells is discussed and the method is applied to three field examples.

A New Analytical Method for Analyzing Linear Flow in Tight/Shale Gas Reservoirs: Constant-Flowing-Pressure Boundary Condition

The interplay between sedimentation and erosion during the late Pleistocene in the Mars-Ursa region, northern Gulf of Mexico, resulted in a complex compartmentalized reservoir. Rapid deposition, directly downdip of the Mississippi River beginning about 70 k.y., quickly filled antecedent topography in the Mars-Ursa region with a thick accumulation of sand and mud called the blue unit. This permeable reservoir was rapidly and asymmetrically buried by thick, mud-rich levees of two channel-levee systems. Both systems plunged from north to south with a steeper gradient than the underlying blue unit. Rotated channel-margin slides present in both channel-levee systems rotated low-permeability, mud-rich levee deposits beneath the sand-rich channel fill. As a result of the channel-levee systems, the east-west hydraulic connectivity of the blue unit decreases progressively from north to south until its eastern and western halves become completely separated.

Seismic geomorphology, lithology, and evolution of the late Pleistocene Mars-Ursa turbidite region, Mississippi Canyon area, northern Gulf of Mexico

Failure analysis of drill pipe: A review

A drilling assembly and an eccentric, adjustable diameter reamer are disclosed. The reamer includes cutter elements mounted on at least a first fixed blade for reaming a previously-formed borehole or for forming a borehole of increased diameter beneath an existing cased borehole. The method and apparatus provide for stabilizing the drilling assembly so that the reamer may be used in back reaming the hole. Retainer means, such as shear pins or spring-biased reciprocating latch members, are provided to prevent premature extension of the reamer's moveable members, including blades and pistons. The shear pins are preferably accessible from the outer surface of the reamer housing so as to expedite field replacement of the shear pins without requiring disassembly of the reamer. The spring-biased latching members repeatedly latch and unlatch so that field replacement is not required, and so that the movable members may be extended and contracted multiple times while the reamer is downhole.

Apparatus and method for drilling and reaming a borehole

/pdf/hydraulic-fracturing-in-particulate-materials-443i9mqdpu.pdf

Hydraulic Fracturing in Particulate Materials

Wells drilled in the deepwater Gulf of Mexico often experience problems with shallow abnormal pressured sands. Successfully drilling through these sands has been an industry wide problem. Shallow water flow problems have caused the industry to junk wells prior to evaluation of any or all well objectives and prevented using discovery and appraisal wells as producers. Shallow water flow problems also caused the loss of the wells at the first Ursa Tension Leg Platform (TLP) site. The Ursa field is located in the deepwater, 3800' water depth, Mississippi Canyon area of the Gulf of Mexico where shallow water flow problems have been severe. The sediments at Ursa contain massive, wet sands that are pressured above a normal seawater gradient at a very shallow depth below mudline. Different techniques have been used while drilling the discovery, appraisal, and development wells to attempt to successfully prevent and control shallow water flow problems. The severe shallow water flow problems at Ursa have been successfully overcome and the shallow batch set drilling program was completed at the second TLP site in mid-1998. Eleven wells, which required five casing strings, have been successfully drilled to below the base of the shallow water flow zones. This paper will discuss the problems encountered during exploratory, appraisal and development drilling at the Ursa field.

Drilling Through Deepwater Shallow Water Flow Zones at Ursa

Because of its location, Ursa field has had more rapid shallow-sediment deposition than other deepwater areas in the U.S. Gulf of Mexico. Common deepwater-shallow-sediment traits are low fracture gradients and pore pressures greater than a seawater gradient. The high pore pressure relative to the fracture gradient causes difficult drilling conditions in the shallow regions of the well.

Drilling through deepwater shallow water-flow zones at Ursa

First Simultaneous Application of Rotary Steerable/Ream-While-Drill on Ursa Horizontal Well

Tool Joint Heat Checking While Predrilling for Auger TLP Project

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Drilling Through Deepwater Shallow Water Flow Zones at Ursa

Drilling through deepwater shallow water-flow zones at Ursa

First Simultaneous Application of Rotary Steerable/Ream-While-Drill on Ursa Horizontal Well

Tool Joint Heat Checking While Predrilling for Auger TLP Project