The Multiwell Experiment Core Program, II

Sattler, A.R.

doi:10.2118/12854-ms

Cited by 4 publications

References 6 publications

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Evaluation and Comparison of Residual Oil Saturation Determination Techniques

Chang¹,

Maerefat²,

Tomutsa³

et al. 1988

SPE Formation Evaluation

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The amount and distribution of residual oil saturation (ROS) are critical parameters for determining whether to apply an EOR process to a reservoir. A brief review of available ROS techniques is presented, indicating advantages, limitations, problems, and possible improvements of each technique. Advantages and disadvantages of each ROS-determination technique are summarized. Screening criteria for determining the best ROS technique under certain well bore or reservoir conditions are presented.This paper also presents results from comparisons of ROS measurements obtained from the literature as calculated from resistivity logs, pulsed neutron capture (PNC) logs, pressure coring, single-well tracer tests, nuclear magnetism logs (NML), carbon/oxygen (C/O) logs, and electromagnetic propagation tool (EPT) measurements. In this study, the ROS measured by each method is compared with that determined by other methods conducted in the same well. The comparison shows that average values of ROS determined by C/O log, PNC-LIL (log-inject-log), and single-well tracer test do not differ statistically when compared with other methods. The resistivity log tends to give higher than average [2 saturation units (s.u.)] ROS measurements, while pressure coring tends to give lower than average (4 s.u.) ROS values. EPT and NML show deviations of about 8 s.U. of ROS values from other methods, which indicates a statistically significant difference. ROS vertical profiles obtained by two different methods from the same well were compared to eliminate the ROS variation resulting from formation depth. The vertical profiles based on ROS zoning and foot-by-foot measurements were studied to provide more "resolution" for comparisons. The results show that discrepancies in measurement methods are more pronounced when vertical profiles are divided into different zones. This could mean that the discrepancies are much greater for some zones than for others. This approach offers the possibility of studying ROS-method discrepancies as a function of different ROS values.

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Evaluation and Comparison of Residual Oil Saturation Determination Techniques

Chang¹,

Maerefat²,

Tomutsa³

et al. 1988

SPE Formation Evaluation

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Laboratory Studies for the Design and Analysis of Hydraulic Fractured Stimulations in Lenticular, Tight Gas Reservoirs

Sattler¹,

Hudson²,

Raible³

et al. 1986

All Days

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This paper was selected for presentauon by an SPE Program Commmee following rewew of mformahon conlamed in an abstract submmed byIhe author(s) Contents of the paper. as presented. have not been rewewed by Ibe Somety of Petroleum Englfieers and are subject 10 correchon by the author(s). The material, as presented, does not necessarily reflect any !JOstlton of the Society of Petroleum Engineers, Its officers. or members Papers presen!ed at SPE meetings are subject 10 pubhcauon rewew by Ed!torlal Committees of [he SOCtety of Petroleum Engineers permm.s!on to COPY IS restncled to an abstract of not more than 300 wcrds Illushat!ons may not be copied. The abstract should contain Conspicuous acknowledgment of where and by whom the paper is presented. Wnle Publ!callons Manager, SPE. P 0 Box 833836, Richardson. TX 75083-3S36. Telex. 730989, SPEDAL. lBSTRACT INTRODUCTION Laboratory studies were used as an aid in Laboratory studies used to help in feeigning stimulation treatments and to assist in were stimulation designs for lenticular, tight gaa sand Lhe analysis of production results. These reservoirs and also to assist in the analysis of malyses were done in conjunction with coastal production results. These studies were done in zone stimulation operations at the Department of conjunction with the stimulation of the Mesaverde Energy's Multiwell Experiment near Rifle, formation at the Depactrnentof Energy's Uultiwell Colorado. A multitreatment stimulation plan was Experiment (W) near Rifle, Colorado.1*2 A designed for the coastal zone because of apparent complete group of pre-and post-frac Laboratory demage to the paludal zone formations in prior studies was done as an integral part of the stimulation operations. The stimulation plan was operation. made to minimize the use of water-based, gelled fluids. Two small stimulations were performed in The fracturing operation were conducted in the same coastal interval: an unpropped nitrogen the yellow coastal sand of the MWX-1 well at gas frac and a propped, nitrogen foam frac. Gas 6425 ft to 6475 ft (1960-1975 m) (Fig. 1). MaLrix production decreased from that of the gas frac permeabilities to gas of this sand are in the few after the nitrogen foam stimulation and formation tenths of a microdarcy range.3-5 The rock is damage was apparent. The laboratory program was extremely tight, among the used to (1) aid stimulation design; (2) help SE% 13867, ProceedirVe of the 1985 SPEfDOE Symposium on Low Permeability Reser-.Frac fluid-matrix rock compatibility.

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Permeability Damage to Natural Fractures Caused by Fracturing Fluid Polymers

Gall¹,

Sattler²,

Maloney³

et al. 1988

All Days

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Formation damage studies using artificially fractured, low-permeability sandstone cores indicate that viscosified fracturing fluids can severely restrict gas flow through these types of narrow fractures. These studies were performed in support of the Department of Energy's Multiwell Experiment (MWX). The MWX program was a coordinated research effort to study methods to evaluate and enhance gas production from low-permeability lenticular reservoirs of the Western United States. Extensive geological and production evaluations at the MWX site indicate that the presence of a natural fracture system is largely responsible for unstimulated gas production. The laboratory formation damage studies were designed to examine changes in cracked core permeability to gas caused by fracturing fluid residues introduced into such narrow fractures during fluid leakoff. Polysaccharide polymers caused significant reduction (up to 95%) to gas flow through cracked cores. Polymer fracturing fluid gels used in this study included hydroxypropyl guar, hydroxyethyl cellulose, and xanthan gum. In contrast, polyacrylamide gels caused little or no reduction in gas flow through cracked cores after liquid cleanup. Other components of fracturing fluids (surfactants, breakers, etc.) caused less damage to gas flows. The results of fluid leakoff tests indicated that polysaccharide polymers caused a filter cake buildup at or near the crack entrance while polyacrylamide polymers did not cause a filtercake buildup within the time period of the tests. For xanthan gum gels filtercake buildup was reduced for gels containing polymer breakers. For gels containing polymer breakers, 100 mesh sand was an effective fluid-loss control agent for narrow fractures. Other factors affecting gas flow through cracked cores were investigated, including the effects of net confining stress and non-Darcy flow parameters. Results are related to some of the problems observed during the stimulation program conducted for the MWX. Introduction The MWX has been an extensive program to characterize and stimulate gas production from low-permeability lenticular gas reservoirs of the Western United States. Three closely spaced wells were drilled into the Cretaceous Mesaverde group in Garfield County near Rifle, Colorado. After extensive geological and geophysical characterization, a series of stimulation treatments were performed in sandstones of the paludal, coastal, and fluvial intervals of the Williams Fork formation at the MWX site. A number of reports have been published which describe the work that has been performed at the MWX site. Core studies indicated that dry core matrix permeabilities to gas at reservoir stress conditions were less than 10 40d and frequently less than 3 40d. At typical levels of water saturation for the reservoir, these values may be reduced by an order of magnitude. Porosities ranged from 3 to 12%. Clays generally averaged less than 10% and were predominantly illite and mixed-layer clays. P. 551^

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The Multiwell Experiment Core Program, II

Cited by 4 publications

References 6 publications

Evaluation and Comparison of Residual Oil Saturation Determination Techniques

Evaluation and Comparison of Residual Oil Saturation Determination Techniques

Laboratory Studies for the Design and Analysis of Hydraulic Fractured Stimulations in Lenticular, Tight Gas Reservoirs

Permeability Damage to Natural Fractures Caused by Fracturing Fluid Polymers

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