AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
A New, Systematic Approach to Achieve Effective Completions in Unconventional Reservoirs
(1) Halliburton, Oklahoma City, OK.
Recent technical papers have highlighted the difficulty of achieving efficient completions in horizontal wells. Although every stage of a horizontal unconventional well was fracture treated, many of the clusters completed in these wells were unproductive, as demonstrated by production logs through these intervals. The economics of a well is negatively affected when a large number of stimulation clusters will not produce. Some data analysis that could preclude unnecessary or unproductive intervals would be useful.
Three real questions arise from analysis of the available data:
1. Is the reservoir capable of delivering fluid (gas, water, or oil) to the wellbore?
2. Is it possible to establish a fracture treatment into a particular productive segment of the well?
3. If a fracture treatment can be established, is the formation sufficiently rigid to retain the geometry of the induced treatment?
Permeability is crucial in the answers to questions 1 and 2. If the rock is incapable of delivering fluid, no fracture treatment will yield production. Rock mechanical properties must be considered in questions 2 and 3. Regardless of the permeability of a portion of the well, if a treatment cannot be established and maintained, that stage will eventually become unproductive. The most common solution to regain production is to refracture these horizontal wells, either in the same perforations or by placing additional perforations between the existing perforations, but the problems afflicting the initial completion quickly return in the recompleted wells.
Recent advances in NMR analysis indicate that a direct relationship between relaxation and permeability can be derived and has been established for many unconventional reservoirs. This permeability establishes a landing horizon that will provide the best completion interval.
Analysis of dipole sonic data in these pilot holes provides vertical and horizontal closure stress. Combining this knowledge with permeability data helps to establish the landing horizon. This data predicts the ability of the reservoir to deliver fluids from these identified permeable sections of the reservoir to the induced fracture treatment.
This paper shows how this data is applied in a systematic way to define the most productive intervals in a well, and provides the best available completion for the well.