Downhole Fluid-Loss Measurements From Drilling Fluid and Cement Slurries
- J.P. Haberman (Texaco Inc.) | M. Delestatius (Texaco Inc.) | D.G. Hines (Dowell Schlumberger) | G. Daccord (Dowell Schlumberger) | J-F. Baret (Dowell Schlumberger)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- August 1992
- Document Type
- Journal Paper
- 872 - 879
- 1992. Society of Petroleum Engineers
- 4.3.4 Scale, 2.2.3 Fluid Loss Control, 4.1.5 Processing Equipment, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.11 Drilling Fluids and Materials, 5.6.4 Drillstem/Well Testing, 1.14.3 Cement Formulation (Chemistry, Properties), 4.3.1 Hydrates, 1.7 Pressure Management, 1.14 Casing and Cementing, 1.6 Drilling Operations, 4.1.2 Separation and Treating, 2.4.3 Sand/Solids Control
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This paper reports on a cooperative effort to demonstrate that direct field measurements of the fluid loss from wells are possible and yield significant results. Four wells in the Mississippi River delta were systematically shut in, and the fluid loss from the annulus was measured both with only mud in the annulus and after cement placement. The wells had extensive intervals of permeable sands, making them well-suited for fluid-loss tests. The results indicated a much lower fluid loss per unit area of permeable sands both before and after cementing compared with routine laboratory testing. Results also indicated that cement fluid loss was controlled mainly by filtration properties of the drilling-fluid mudcake.
One fundamental requirement for a successful cementing job is the complete displacement of drilling mud during cement placement. Means to achieve this include conditioning the drilling mud and using preflushes, casing movement, and centralizers. These procedures displace the mobile mud and, if applied aggressively, most of the gelled mud.
The effect of these procedures on the drilling-mud filter cake has caused controversy in the industry for many years. Laboratory studies have shown that mudcake is difficult to erode, and when it is partially removed by the tangential flow, the filtration rate is not modified. However, when turbulent spacers displace the mud at high rates or when mechanical scratchers are used, filtration rates can increase significantly.
A fundamental question has been whether mudcake maintains its integrity and low permeability sufficiently during the cementing process to control the fluid loss from cement slurries or whether the filtration properties of cement slurries control the overall fluid loss.All the results before this work were obtained by laboratory testing or computer simulations and had not been compared with actual field fluid-loss measurements. The objectives of this project were to measure in the field fluid loss from the annuli of wells before and after the casing was cemented, to answer some of the questions raised, and to develop measurement techniques that could be used for further studies.
Downhole fluid loss (DHFL) was measured (after the intermediate casing was run) by closing in the casing annulus with the annular blowout preventer (BOP) and pumping water into the annulus through the surface casing valves. Measurements were made several ways to obtain the maximum value from the results.
(1) To determine the accuracy of the measurements, the DHFL measured by a pressure-decline method was compared with the DHFL measured by a fluid-injection method.
(2) To determine the effect of cement placement on the mudcake, the DHFL before cementing was compared with the DHFL after cementing.
(3) To determine the effect of cement fluid-loss-control additives, the DHFL with additives in the cement slurries was compared with the DHFL without additives.
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