WO1984004927A1

WO1984004927A1 - Drilling mud containing clays and lignin from bark

Info

Publication number: WO1984004927A1
Application number: PCT/NO1984/000024
Authority: WO
Inventors: John Hoeye
Original assignee: John Hoeye
Priority date: 1983-06-09
Filing date: 1984-06-08
Publication date: 1984-12-20
Also published as: NO153373C; NO832101L; NO153373B

Abstract

Drilling mud which in addition to clay minerals also contains bark lignin. The use of bark lignin, particularly sodium lignin, as auxiliarly colloid in drilling, particularly together with clay minerals.

Description

"Drilling mud containing clays and lignin from bark."

It is known that ordinary wood lignin has been tried in drilling mud as a possible diluent and water- loss reducing agent (colloid), but without success, primarily because the lignin colloid particals are too large to be entirely satisfactory and partly because there is little wood lignin on the market which may be used at all. With respect to wood lignin, it is only lignin from the soda pulp process which is useful at all, while lignin from sulfite waste liquor (lignin sulfonic acids) and lignin from the sulfate pulp process are completely unsuitable. Thus, although it is possible to use lignin from the soda pulp process, such lignin is far from satisfactory.

Ordinary wood (sulfate/soda) lignin has according to the Pulp and Paper Magazine of Canada, 73, 1972 an

2 internal surface of only 10-65 m /g. Lignin from the sulfate process will in low pH mud generate an unpleasant smell of H₂S from sulfide groups in this lignin formed during the sulfate (including sulfide) pulping process. The rheological (viscosimetric) values in the mud should be relatively low for several reasons. It is easier to pump the mud at a low yield point value and thereby also easier to separate the loosened materials by sedimentation and shaking sieve, and since the gel- values at the same time also become lower, this will result in a better distribution of the loosened material in the mud on its way up and also better rinsing and cooling of the drilling bit, and low gel values will also make it easier in case of so-called "loss of circulation" or when the drilling is stopped.

It has now been found that so-called bark lignin, prepared according to Norwegian Patent No. 128.174, has a colloid particle size of 2-llμm and an internal surface

2 of 280-405 m /g (determined by a phase contrast method) which fits very well with most types of bentonites and other clay materials such as attapulgite, montmorillonite

OMP and sepiolite etc. which are used as main colloid for oil drilling. All these clays have a particle size of 60-100 μra, and it is specifically to fill the voids or the pores between these clay particles that it is necessary to use auxiliary colloids with colloid parti¬ cles between 2-11 μm, just like Na-lignin from bark. Further, bark lignin is quite resistant against fermen- tation and against all the chemicals used and may also resist temperatures up to 230°C. It may also be men¬ tioned that bark lignin (Na-lignin) contains 8,14% phenolic OH groups determined according to Høye's ferric chloride method described in Norsk Skogindustri, volume 30, 8/76, p. 243. The fenolic groups bind troublesome heavy metals in the mud.

Bark lignin may be used at pH values down to 5. Bark lignin which is completely free of heavy metal contaminations.such as chromium, has now been tested as auxiliary colloid (diluent) and water loss reducing agent compared with a well known chromium free diluent "Aqua Magic" in sea water mud. "Aqua Magic" is a type of lignite which is rather something between brown coal and peat. The lignite is "dissolved" in NaOH, and i.a. colloidal silica has been added.

As a starting mud was used 12.5% by weight of attapulgite and 1.25% by weight of bentonite in sea water The pH value of the mud was adjusted to 10. O± 0.2 with NaOH. Auxiliary colloid was added to the starting mud, and the mud was stirred for 5 minutes. The pH was again adjusted to 10.0 ± 0.2. The mud was then stirred for additional 5 minutes and examined.

The mud was aged at 80°C for 24 hours. After cooling to room temperature the pH value was adjusted to 10.0 ± 0.2, and the mud was stirred for 5 minutes and examined. All experiments were carried out in accordance with "API recommended practice, standard procedure for testing rilling muds (fluids)".

The results are given in the following table:

TABLE

Test of bark lignin and "Aqua Magic" in sea water mud

Amount added in grams Bark lignin "Aqua Magic" per 350 ml of mud pH adjusted to 10.0 1 2 5 10 I 2 1 6 10

Apparent viscosity, cp a) 99 55 28 24 a) a) a) a) 124

Plastic viscosity, cp 0 12 8 21 1

"yield point" kg/m² 9,65 4,2 1,95 0,29 11,96

2 Gel strength, 10 sec. kg/m 3,65 2,24 1,46 0,39 4,39

2 Gel strength, 10 min. kg/m 3,8 2,58 1,32 1,27 4,29

Heat treatment; 24 hours at 80°C

(pH was adjusted to 10.0 after the heat treatment)

Apparent viscosity, cp a) 96 33 20 13 a) a) 129 81 66 Plastic viscosity, cp 0 8 20 11 25 14 15

"yield point" kg/m² 9,3 2,39 0,98 0,15 10,10 6,54 4,93

2 Gel strength, 10 sec. kg/m 3,32 1,22 0,34 0,05 3,81 2,49 2,00

2 Gel strength, 10 min. kg/m 3,37 1,51 0,73 0,49 3,66 2,49 1,81

API-filter loss ml, room temperature 90 80 69 67 61 90 90 84 84 77 a) too thick to be measured

T \

Gel 10 sec. and Gel 10 min. mean that the viscosimeter is stopped for 10 sec. and 10 min. respectively, and the viscosimeter reading upon new sta 80 is registered. The Gel values represent a good measure o the thixotropy of the mud, which is of great importance the mud circulation must be stopped, for instance during the addition of new joints or particularly during so- called "loss of circulation". The ability to a certain 85 gel formation (thixotropy) is then important in order to prevent the loosened material in the mud from sinking downwards in the bor hole and clog the entire passage between the drill pipe and the wall of the well. Since the gel values of the mud do not really influence the 90 pumping, it is better to have a certain thixotropy in the mud than to have a sufficiently high yield point to inhibit a corresponding "precipitation" of loosened material in case of lost circulation. A high yield point will to a great extent prevent the pumping of 95 the mud and make it unnecessary energy-requiring.

On the enclosed figures 1-3 A represent bark lignin, while B represents "Aqua Magic".

The functions of the auxiliary colloid (the thinner) in drilling mud is primarily to reduce the 100 viscosity and the gel strength of the mud, and these effects appear from the above table and the figures. On figure 1 the apparent viscosity of sea water mud has been plotted against the concentration of auxiliary colloid in the mud. It will be seen that 105 A reduces the apparent viscosity much more than B. The changes in gel strength in the mud by increasing the concentration of auxiliary colloid is illustrated on figure 2, where it will be seen that A also reduces the gel strength of the mud more effec- 110 tively than does B.

On figure 1 and 2 there are given the initial results as well as the results after aging for 24 hours at 80°C. However, with B the mud was initially too thick to be measured, and in the table and on the figures

115 only the results after the heat treatment have been given. From the table and figure 3 it will also be seen that the auxiliary colloid has a positireeffect on the filter loss from the mud. It will be seen that the best effect is obtained with A.

120 A suitable form of bark lignin is sodium lignin, which is suitably prepared by the process according to Norwegian Patent 128.174 as mentioned above.

"BURE

OMPI

Claims

1. Drilling mud containing clay minerals, c h a r a c t e r i z e d i n that it also contains

125 bark lignin.

2. The use of bark lignin, particularly sodium lignin, as auxiliary colloid for drilling.

3. The use according to claim 2 of bark lignin together with clay minerals as main colloid in oil

130 drilling.